The Skim Insider’s Guide
Everything we know about Skim in one document: what it costs, its grades, getting a refund, getting help and what else to look at. Read it here, or keep a copy.
Skim
The Insider’s Guide
Free PDF reader and note-taker for Mac, built for papers
Every plan, grade, refund rule and rival among PDF editors, read from Skim’s own pages.
Made by Skim project (SourceForge) · checked Nov 13, 2026 · toolgpa.com
Contents
- 01WelcomeWhat it is, who it suits, its grades and the ten things to know first
- 02What it costsEvery plan, the free plan, ways to pay less and how prices have moved
- 03What it doesIts main features, where it runs, what it works with and who makes it
- 04Where it standsIts grades against its category, and whether to keep it or make your own
- 05The alternativesThe tools it is most often weighed against, side by side
- 06Quick answersThe questions people ask about it, each answered in a line or two
- 07About ToolGPAWho made this guide, what else is on the site, and how to cite it
ToolGPA put this guide together from Skim’s own pages, its app-store listings and our grades. Every fact in it is on Skim’s page too, where it is kept up to date. Checked Nov 13, 2026.
Part 01 · Overview
Welcome
What it is, who it suits, its grades and the ten things to know first
2.8
GPA, above 31 of the 45 other PDF editors we grade
Skim is a free, open-source PDF reader for macOS made for reading and annotating scientific papers. It supports notes, highlights, snapshots and a reading bar, and it links with LaTeX and BibDesk. It annotates documents; it is not an editor for changing the existing text or pages.
To get you started, here are 8 things to know about Skim, taken from its own pages and our grades.
It does not edit text or fill in forms, and it runs on Mac only.
- 1
Best for reading and annotating papers on a Mac
Skim is a free, open-source PDF reader for macOS built for reading and annotating scientific papers, with LaTeX and BibDesk links.
- 2
It is free
Skim has no paid plan at all. Everything: the whole app is free to download and use.
- 3
It runs on macOS
macOS.
- 4
Notes and highlights
Add and edit notes, highlight text with one-swipe modes, and view all notes and highlights in one list.
- 5
Snapshots and reading bar
Keep snapshots of other parts of a document for reference and focus a line at a time with a reading bar.
- 6
Navigation
Move around with the table of contents or thumbnails, with a visual history and previews of internal links.
- 7
A 2.8 GPA, above 31 of 45
That is against the other PDF editors we grade, on value, the free plan, features, ease of use and platforms.
- 8
Keep it
Skim is free, so making your own would save you nothing.
Skim at a glance
- Pricing
- Free
- Free plan
- Yes
- Free trial
- None stated
- Runs on
- macOS
- Made by
- Skim project (SourceForge)
- Category
- PDF Editors
- Our grade
- 2.8 GPA, good
The report card
Best for reading and annotating papers on a Mac
Skim is a free, open-source PDF reader for macOS built for reading and annotating scientific papers, with LaTeX and BibDesk links. It does not edit text or fill in forms, and it runs on Mac only.
| Subject | Grade | Comment |
|---|---|---|
| Value for money | A | Free to download and use, with no paid tier, so it sits well under the cheapest quarter of PDF tools. |
| Free plan and trial | A | The whole app is free, with nothing held back. |
| Features | C | Notes, highlights, snapshots, a reading bar and AppleScript. It does that job fully, but it is a smaller one: the listing shows no text editing or form filling. |
| Ease of use | B | No store rating is on record, but it is a program you install and open, with nothing to set up. |
| Platforms and integrations | D | macOS only, version 1.7.19 needing macOS 10.13 or higher. There is no Windows, phone or web version. |
An A is worth 4 points, a B 3, a C 2, a D 1 and an F nothing. The GPA is the average of the five.
Who Skim is for
- Fits if you read and mark up papers on a Mac, especially with LaTeX or BibDesk
- Works for anyone who wants a free annotator and not an editor
Who it is not for
- Skip it if you use Windows, Linux or a phone, as it runs on Mac only
- Too light for editing text or filling in forms, since neither is listed
- Watch out: support is a wiki, mailing lists and bug trackers, not a help desk
- Tight if your Mac is old, because the current version needs macOS 10.13
Good to know
Good for
- Researchers reading and annotating papers on a Mac
- LaTeX users who need synced source and PDF views
- Anyone who wants a free annotation tool
Worth knowing
- Mac only; current version 1.7.19 needs macOS 10.13 or higher, with older versions listed for older systems.
- It is a reader and annotator, with no listed tools for editing existing text or filling in forms.
- Support runs through a wiki, mailing lists and bug trackers rather than a company help desk.
Part 02 · Pricing
What it costs
Every plan, the free plan, ways to pay less and how prices have moved
Free
No paid plan at all
Skim is free to use.
Free to download and use, with no paid tier, so it sits well under the cheapest quarter of PDF tools.
Skim
$0
Free to download; the site lists no paid plans or licence fees.
The free plan
Everything: the whole app is free to download and use.
Read from skim-app.sourceforge.io on Nov 13, 2026.
Part 03 · Features
What it does
Its main features, where it runs, what it works with and who makes it
1
Place it runs: macOS
Free PDF reader and note-taker for Mac, built for papers. Here is what it does, as its own site describes it, and what it covers: open source, notes, highlights, pDF editing.
Notes, highlights, snapshots, a reading bar and AppleScript.
- Notes and highlights
- Add and edit notes, highlight text with one-swipe modes, and view all notes and highlights in one list.
- Snapshots and reading bar
- Keep snapshots of other parts of a document for reference and focus a line at a time with a reading bar.
- Navigation
- Move around with the table of contents or thumbnails, with a visual history and previews of internal links.
- Presentations
- Present a PDF full screen with built-in transitions, and crop pages with the smart cropping tools.
- Export and scripting
- Export notes as text and automate with extensive AppleScript support.
- LaTeX and reference tools
- Works with LaTeX through SyncTeX and PDFSync, and integrates with BibDesk and other third-party apps.
Where it runs
- macOS
What it works with
- BibDesk
- LaTeX
- SyncTeX
- PDFSync
- AppleScript
Skim is made by Skim project (SourceForge).
Part 04 · Standing
Where it stands
Its grades against its category, and whether to keep it or make your own
31/45
Other PDF editors it is graded above
Skim's GPA of 2.8 is higher than 31 of the 45 other PDF editors we grade, and level with 7.
It stands best on free plan and trial (A, above 39 of 45) and worst on platforms and integrations (D, above 0).
Skim has no paid plan.
On features, ease of use and platforms it scores 2.0 out of 4. Nothing scores higher for less, though at least one tool matches that score at a lower price.
Each grade against the category
Every bar is all 46 PDF editors we grade, cut by the letter each got. Skim’s own letter is outlined.
- AValue for moneyAbove 31 of 45
- AFree plan and trialAbove 39 of 45
- CFeaturesAbove 2 of 45
- BEase of useAbove 11 of 45
- DPlatforms and integrationsAbove 0 of 45
Price against what you get
Each dot is one of 32 PDF editors. Further left costs less; higher up scores better on features, ease of use and platforms. Skim is the marked dot.
What paid plans start at, a month (each step along is roughly double) →
Keep it, or make your own?
Whether this is something you could build for yourself with an AI app builder, and what you would give up.
Keep it
Skim is free, so making your own would save you nothing.
And it is not the kind of software a weekend replaces. It is one of the better ones too: its GPA of 2.8 is higher than 31 of the 45 other PDF editors we grade.
What you could make
- Highlights and notes: an app builder makes these well.
What you could not
- Editing the text inside a PDF without breaking its layout.
- A real app for macOS. Something home-made would be a web page.
- It plugs into other products, BibDesk, LaTeX and SyncTeX among them.
What this rests on. Skim’s listing: what it does, where it runs, what it plugs into and what it costs. It is a judgement about the kind of software this is. We have not built a replacement for it, and making your own means looking after it too. How we decide, and every tool’s verdict.
Part 05 · Alternatives
The alternatives
The tools it is most often weighed against, side by side
PDF Expert, PDF Reader Pro, Xodo, PDFgear and PDF Annotator
The 5 tools Skim is most often weighed against, with where each one differs from it.
- 2.4GPA
PDF Expert
Free plan · from $79.99/yr
PDF reader and editor for Mac, iPhone and iPad from Readdle.
- Only PDF Expert lists an iOS app.
- Skim is open source, according to its own site.
- Skim also covers notes and highlights.
- 3.0GPA
PDF Reader Pro
Free plan · from $59.99/yr
PDF viewer and editor for Mac, Windows, mobile and web.
- Only PDF Reader Pro lists a web app.
- Only PDF Reader Pro lists Windows, iOS and Android apps.
- Skim is open source, according to its own site.
- 2.2GPA
Xodo
Free plan · from $7.99/mo
PDF tools on web, desktop and mobile, sold separately or as a suite.
- Only Xodo lists a web app.
- Only Xodo lists Windows, Linux, iOS and Android apps.
- Skim is open source, according to its own site.
- 3.4GPA
PDFgear
Free
Free PDF editor for desktop, mobile and web with an AI copilot.
- Only PDFgear lists a web app.
- Only PDFgear lists Windows, iOS and Android apps.
- Only PDFgear lists a browser extension.
- 2.4GPA
PDF Annotator
Free trial · from $79.95 one-time
Windows PDF markup and note-taking app sold as a perpetual license.
- Skim has a free plan. PDF Annotator does not, though it has a free trial.
- Only Skim lists a macOS app.
- Only PDF Annotator lists a Windows app.
Part 06 · Questions
Quick answers
The questions people ask about it, each answered in a line or two
12
Questions, each answered in a line or two
The short version of everything above, for when you only need the answer. Each one is told in full in its part of the guide.
Is Skim free?
Yes. Skim is free to use.
How much does Skim cost?
Skim lists one plan. Skim: $0.
What platforms does Skim work on?
Skim is available on macOS.
Does Skim have an Android app?
No Android app was listed when its pages were read on Nov 13, 2026. Skim is listed for macOS.
Does Skim have an iPhone app?
No iPhone app was listed when its pages were read on Nov 13, 2026. Skim is listed for macOS.
Is Skim open source?
Yes. Skim is open source, according to its own site.
What does Skim integrate with?
Skim's listing names BibDesk, LaTeX, SyncTeX, PDFSync and AppleScript.
Who makes Skim?
Skim is made by Skim project (SourceForge).
What are the alternatives to Skim?
The closest alternatives to Skim in our directory are PDF Expert, PDF Reader Pro, Xodo, PDFgear and PDF Annotator.
How does Skim compare with other PDF editors?
Skim's GPA of 2.8 is higher than 31 of the 45 other PDF editors we grade, and level with 7.
Is Skim good value for money?
ToolGPA grades Skim A for value for money. Skim has no paid plan.
Could I make my own version of Skim?
Skim is free, so making your own would save you nothing. And it is not the kind of software a weekend replaces.
Where this guide comes from
The prices, plans, platforms and features were read from Skim’s own pages on Nov 13, 2026, and the grades were given on Nov 13, 2026. Graded from this listing, whose facts were read from Skim's own pages on 13 November 2026. Not based on using the product, and shorter than our full reviews.
Every tool we list gets five grades, A to F, each with its reason, and a GPA that averages them. How each is decided is at toolgpa.com/grades. This guide is ToolGPA’s own work; it is not made, paid for or approved by Skim project (SourceForge). Prices change, so check skim-app.sourceforge.io before you buy.
Part 07 · About
About ToolGPA
Who made this guide, what else is on the site, and how to cite it
7,721
Tools graded, in 95 categories
ToolGPA grades software the way a school report grades a pupil: five subjects, a letter for each with the reason written beside it, and a GPA that averages them. Prices, plans and platforms are read from each maker’s own pages and dated, so you always know how fresh a figure is.
Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Every tool on the site has a guide like this one, free to download and pass on. It all lives at toolgpa.com.
7,721
tools graded
95
categories
739
price changes on record
579
apps priced in 12 countries
What else is on toolgpa.com
- Skim, kept up to dateEverything in this guide, with prices and grades as they are todaytoolgpa.com/tools/skim
- How grades are givenThe rules behind every letter and every GPAtoolgpa.com/grades
- Value chartsWhat each tool costs against what it scores, for every categorytoolgpa.com/charts
- CompareAny two tools side by side, plan by plantoolgpa.com/compare
- Price changesEvery price rise and cut on record, each with its sourcetoolgpa.com/price-changes
- Prices by countryWhat apps cost on the App Store in 12 countriestoolgpa.com/prices-by-country
- Pay lessEvery public discount: yearly billing, students, nonprofitstoolgpa.com/save
- Keep or makeWhich tools are worth paying for, and which you could build yourselftoolgpa.com/keep-or-make
Scan for the live page
Prices and grades as they are today
Quoting this guide?
Please name ToolGPA and link to the live page, so readers can check the figures for themselves:
ToolGPA, "Skim: The Insider's Guide", checked Nov 13, 2026. https://toolgpa.com/tools/skim
Know someone choosing between PDF editors?
Send them this guide: toolgpa.com/tools/skim/guide
ToolGPA elsewhere: youtube.com/@toolgpa
See our other guides
The best-graded PDF editors after Skim, each with an Insider's Guide of its own.
- PDF Editors Insider's GuideEvery one of the 46 PDF editors we grade, compared
- PDFgear Insider's GuideFree PDF editor for desktop, mobile and web with an AI copilot3.4 GPA
- Stirling PDF Insider's GuideOpen-source PDF editor you can run on your own machine or server3.2 GPA
- Online2PDF Insider's GuideFree browser tool to convert, merge, edit, compress and unlock PDFs3.0 GPA
Choosing software? Every tool graded, every price dated.
Compare tools at toolgpa.com ›Everything in this guide is ToolGPA’s own summary of what Skim’s pages, its app-store listings and public reviews said on the dates shown. Grades are our judgement under the rules at toolgpa.com/grades. Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Skim is a trademark of its owner, and this guide is not made, paid for or approved by Skim project (SourceForge). Prices and plans change: check skim-app.sourceforge.io before you buy.