SUMMARY/Cheat Sheet (2014 Jan 18)
Gnome or other Desktop Environment (DE)? Use Xournal for highlighting, note-taking, etc.
For smaller text size comments, use Flpsed, which allows you to adjust size of the text you are superimposing over the PDF background itself (good for filling out non-form PDF permission sheets, applications, etc. Xournal’s text can sometimes be too large and clunky to fit in the space provided in PDF sheets/forms). Update: Ha! Somehow I missed it. You can easily change the font size and font type in Xournal. So no need for Flpsed.
KDE? Consider using Okular. In non-KDE, may not be worth it. Dunno. Not sure how well it saves changes. The only thing that is clearly superior is the fact that if you have a text pdf, its highlighting can be straight/with the line, whereas in Xournal, highlighting is freehand, and so will be less neat visually. [If you must use Okular in GNOME and can’t find it from your Gnome-shell, use Alt+F2 –> “okular” and it will open.]
For saving changes permanently, you might need to EXPORT as PDF, not save as PDF.
For including signature, best to take a picture of your own signature, use GIMP (Photoshop) to make an image (export as .jpg), using contrast and brightness to ensure a pure white background (or else it just looks bad). Then crop and reduce pixels to a small size to fit in “signature” boxes in pdf forms/sheets. Then just copy the image and paste it into your pdf form (opened via GIMP), and export as pdf.
Note: Xournal, flpsed, okular, pdftk (can combine and rotate PDF pages), pdfsam (good for mashing together separate PDFs) should all be easily located in your apt (or yum?) repo’s. One can also easily convert PDF and JPG in bash/shell natively. For more options in GNU/Linux (including stuff with WINE, see this site.
(Actual messy article below…)
YOU DON’T NEED ADOBE BLOAT-READER ANYMORE! You don’t even need Wine or Foxit anymore for GNU/Linux. Use native and free (libre) and open tools like Okular or Xournal!
UPDATE (2013 Aug 17): FLPSED is excellent for adding text on top of a PDF. This is great for PDF “forms” (without form boxes…) that you want to fill out electronically; this trumps Xournal in that YOU CAN CHANGE FONT SIZE, with the smallest font being 8pt. There are other options for those who simply want to write over a PDF. See this link for more info.
UPDATE (2013 Apr 24): Due to ease of use in GNOME (and certainly other non-KDE desktop environments), Xournal has now become my weapon of choice, especially, given the option to either save changes separately or export them as a pdf, which was made known to me thanks to my commentor Paul (see below). This makes it quite robust and easily transferrable in cross-platform situations. I have also been able to use GIMP‘s ability to export as PDF in order to include a picture of my handwritten signatures in pdf forms (though this would be unnecessary if you had a stylus, as you can sign your pdf using the pen function in Xournal and then export as pdf). Though given GIMP’s limitation of importing one page at a time from the pdf, The catenate feature in PDFTK is extremely helpful.
You may remember my post about the built-in invert-colors function in the lightweight, pdf reader Evince, a default for many (GNOME-based?) GNU/Linux distros. (Or if you care about inverting screen colors, check out this post.)
Well, what if you wanted to annotate or type or highlight? Okular is definitely the weapon of choice. (You can also use Xournal for annotating pdf’s, though the edits are saved in a separate xournal file, which may be exactly what some people want…also great for stylus tablet note-taking in general…) It can read highlighted annotations/comments, and it can even separately delete comments. It is very nice and easy to easy to use. Simply open a document, and if there are already annotations or highlights, simply right-click to view comments or delete!
To add annotations, comments, highlights, text, etc., simply go to the Tools –> Review tab (or press F6). It is very easy to use.
NOTE: You must save using the “Save as…” function to save your annotations. This also applies to filling out forms. If you do not see forms, go to View –> Show Forms. Remember, if you want other non-Okular pdf readers to read your form data, you must “Save as…”. Even if you see it in Okular, the changes won’t show up in Evince, for example, until you “Save As…”
NOTE (2): If you want to highlight in another color, simply highlight first in yellow (default) color, and then right click the Annotation (i.e. the highlighting) and select Properties. From there, choose your preferred color.
UPDATE (2013 Mar 18): There may be some more required to send annotations to friends. See Okular’s official FAQs. It is quite helpful. Basically, it saves annotations for the owner of the comments itself. Therefore, you may have to save it as a “Document Archive.” But it reads annotations fine.
UPDATE (2013 Mar 26): It may slightly buggy in Debian Wheezy (my distro) under Gnome 3. Of course, if annotating pdf’s are non-negotiable and have first priority, I think installing the popular KDE Desktop environment would probably smooth out problems. Xournal is also good, and it saves the xournal file right next to your pdf file. So presumably, you can share your annotations without fail by simply sending your pdf and your xournal file, provided the person you want to share with has xournal. But at least you know that xournal and GNU/Linux is free in liberty and cost; it’s not like you would send a .doc or .pptx file, essentially forcing people to pay for a Windows license and spend an exorbitant amount on a stupid Office suite that will be outdated in 3 years (and did you know that new MS Offices can’t actually support its own older formats? That’s why you shouldn’t use MS Office. But I digress)
If I missed anything, or you just feel like sharing or asking something, please comment below.
UPDATE (2013 Apr 17): Now in a text-based pdf, Okular clearly wins in being able to highlight text (so the highlighting is straight and everything). However, given portability and consistency, I am now using Xournal. For anyone who wants to share annotations, Xournal is the way to go. It costs nothing to download (GNU/Linux and Xournal are free in price and liberty). And it is easy to view annotations. One PDF file, one xournal file.
UPDATE (2013 May 1): Of course, Okular also has an export as pdf option, so that may be the way to go to save annotations (though they will not be editable, I don’t think). And, random note: to change default highlighter/pen colors, simply highlight what you want, right-click –> Properties –> voíla!
UPDATE (2013 May 10): This may be common knowledge or it might not. If you cannot find Okular in Gnome, it’s because it’s not integrated with Gnome. Therefore, to open it, just press Alt+F2 and then enter the command “okular”. This works in terminal, too, and you will also see Okular when you right-click a pdf file.