6

I occasionally receive PDFs on which I want to mark comments, or some points/segments of which I want to annotate somehow - similarly to what I would do with printed PDFs.

This does not mean editing the contents - which stays just as it is - only addition of (clearly differentiable) comments - "red pen" style - on the page.

So - I want a piece of software which does this.

Required features:

  • Works on Linux
  • GUI of course
  • Does not mess up the layout of the PDF (i.e. additions-only)
  • Reasonable responsiveness on "heavy" and long PDF documents

Note I haven't listed a license requirements

Desired features:

  • Gratis
  • Libre license
  • Can save the PDF-cum-comments as another PDF file, which will display properly, with the comments, in a typical PDF reader
  • Actively maintained
  • Offers extra functionality when noticing the PDF was created a certain way, e.g. with LaTeX, or LibreOffice, or Microsoft Office etc.
  • Supports both comments and annotations
  • Supports multiple comment authors (e.g. with different color comments)
  • Doesn't make it easy to edit the PDF when I don't want to edit it.
  • Allows extracting/saving the comments/annotations as plain text or some other format convertible to plain text.
  • Doesn't make it easy to edit the PDF when I don't want to edit it. – What do you mean by this? – Wrzlprmft Sep 16 '17 at 19:29
  • I mean, that I can't, say, click someplace near to where I want to put my comment and find myself with an edit box for the PDF's text line, for example. – einpoklum Sep 16 '17 at 19:51
3

So far I have been using Xournal for this purpose and I am quite happy with it. It essentially allows you to draw on top of the PDF using text and primitive drawing routines.

Regarding your criteria:

  • Linux – yes
  • GUI – yes
  • additions-only – yes
  • responsiveness – I haven’t had any challenging cases yet, but so far everything works fine.
  • gratis – yes
  • Libre license – yes, GPL
  • Can save the PDF-cum-comments as another PDF file – yes, with some people using exotic software had problems with my PDFs, but those could be fixed by using a PDF printer instead of the native PDF exporting function.
  • Actively maintained – yes, last update was two months ago
  • Offers extra functionality when noticing the PDF was created a certain way – no
  • Supports both comments and annotations – not really. You draw on the PDF, so the comments do not make use of a special PDF functionality intended for this purpose.
  • Supports multiple comment authors (e.g. with different color comments) – Makeshift. You can comment with multiple colours, but there is no explicit collaborative functionality or similar that I am aware of.
  • Doesn't make it easy to edit the PDF when I don't want to edit it. – Yes, editing the PDF’s text is impossible.
  • Allows extracting/saving the comments/annotations as plain text or some other format convertible to plain text. – Not that I am aware of.
  • So, the GUI is not super-convenient, but it gets the job done. Thanks! ... keeping this open in the hope of something which doesn't make me curse my mouse clicking inaccuracy all the time... – einpoklum Sep 16 '17 at 20:52
2

I would suggest taking a look at Elsevier's Mendeley research paper sharing and management software, and its desktop client specifically. Note that it is a lot more than just a PDF annotation tool it is a research tool that covers a lot more areas.

It allows you to annotate PDF files with:

  • General Notes i.e. notes on the whole file
  • Sticky Notes i.e. notes with specific locations
  • Text Highlights in multiple colours
  • Area Highlights in multiple colours

All annotations are tagged with who added them & when.

Required features:

  • Works on Linux desktop client: Yes & Windows & Mac OS There is also a web interface and iOS/Android apps.
  • GUI of course Yes
  • Does not mess up the layout of the PDF (i.e. additions-only) Yes
  • Reasonable responsiveness on "heavy" and long PDF documents I have not had any problems

Desired features:

  • Gratis Yes for the Free Account with some limitations currently 2GB personal document storage, up to 5 private groups of up to 25 people with up to 2GB of storage across all groups. Additional storage via paid plans
  • Libre license No this is a commercial tool aimed specifically at academia
  • Can save the PDF-cum-comments as another PDF file, which will display properly, with the comments, in a typical PDF reader Yes "Export to PDF" does this giving you a choice of exporting the annotated document or just the annotations
  • Actively maintained Yes
  • Offers extra functionality when noticing the PDF was created a certain way, e.g. with LaTeX, or LibreOffice, or Microsoft Office etc.
  • Supports both comments and annotations Yes
  • Supports multiple comment authors (e.g. with different color comments) Yes You can select colours and all comments & highlights are marked with who & when.
  • Doesn't make it easy to edit the PDF when I don't want to edit it. Yes The comments and highlights are stored separately from the PDF the original file does not get changed at all.
  • Allows extracting/saving the comments/annotations as plain text or some other format convertible to plain text. Yes You can use the tool to export to several academic formats (BibTex, Research Information Systems & Endnote XML) - there is also a GPL python tool Menotexport available for exporting to text files which is both command line & GUI based last update to Menotexport at the time of writing was 8 days ago.
  • This is great, except for the license and its being by... I shudder to even write their name... Elsevier. +1 of course. – einpoklum Sep 17 '17 at 6:57
  • @einpoklum If I knew of a FOSS package that was anywhere near as good then I would recommend that but as it is .... – Steve Barnes Sep 17 '17 at 10:04
  • If it weren't Elsevier, then ok, but it's just that they're so evil :-( – einpoklum Sep 17 '17 at 10:30
2

Okular supported annotations for some time, but since recently, you can also save the annotated PDF using the native PDF annotation format. You can mark specific text passages and add a comment to this; you can also place comments not anchored to a specific text and draw freehand or straight lines, polygons, and ellipses. I recently used this for annotating proofs of a paper and reports I graded and it could do everything I wanted.

Regarding your criteria:

  • Linux – yes
  • GUI – yes
  • additions-only – yes
  • responsiveness – I only tested short documents so far.
  • gratis – yes
  • Libre license – yes, GPL
  • Can save the PDF-cum-comments as another PDF file – yes, since version 0.15, requiring Poppler 0.20 (according to several sources)
  • Actively maintainedyes
  • Offers extra functionality when noticing the PDF was created a certain way – no
  • Supports both comments and annotations – yes
  • Supports multiple comment authors (e.g. with different color comments) – Each comment shows its author. Different colours are not supported.
  • Doesn't make it easy to edit the PDF when I don't want to edit it. – Yes, modifying the underlying PDF is impossible.
  • Allows extracting/saving the comments/annotations as plain text or some other format convertible to plain text. – Yes, Okular stores annotations in an XML format in your config files (.local/share/okular/docdata/ for me).
  • I should really give this another try, after being basically (though not perfectly) satisfied with Xournal so far. – einpoklum Dec 3 '18 at 20:57
  • ... after giving it another try, this doesn't cut it. It's very difficult to place text onto the PDF (which is the basic functionality I'm after): You can only put it in a colored box; you can move it after insertion; it defaults to an annoying background yellow; you cant make the background transparent without making the text transparent as well... In short - anything is better than this. – einpoklum Dec 5 '18 at 11:08

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