The Portable Document Format (PDF) has become the de facto standard for document distribution as it ensures that the distributed text and images can be read or printed appropriately under a variety of platforms. If I recall correctly, it must have been over 8-9 years since I had first searched the web for a PDF viewer that would offer basic PDF editing capabilities. Basic editing capabilities should be translated to providing the user with the ability to highlight, bookmark and take notes inside the PDF document. Of course, there are many high quality commercial PDF editors out there, but many users (including myself) believe that, since the PDF format has gained so much popularity, simple annotating capabilities, such as text highlighting, should be part of a free viewer’s core functionality.

There are many ways you can edit pdf files in Linux, but, the overwhelming majority of them includes lengthy procedures that just end up wasting your time. One program that has performed better than all the others I have tried so far is Xournal. Xournal is not actually a PDF annotator/editor. As the author states:

Xournal is an application for notetaking, sketching, keeping a journal using a stylus.

This software has not been designed for PDF annotation. This feature is simply a side-effect of xournal’s main function, which is notetaking using a stylus. Xournal makes the annotation of a pdf file possible by loading the document as an image and letting you use its sketching tools on a separate layer on top of that of the pdf document. It can finally merge the layers into a single one and save the document as an annotated PDF file, while preserving the original text.

Taking into account that PDF annotation is not Xournal’s purpose of existence, one could say that it does this job quite well. But in comparison to other professional PDF editors, it turns out that it is not as efficient. This is because xournal can only load the PDF document as an image. For instance, when the user tries to highlight a line of text, xournal cannot recognize the text boundaries and use them as a guide, so to help the user highlight that particular line with ease. The user still has to draw a perfect line on top of the actual line of text in order to highlight it.

I admit that when I first tried to highlight some text in a pdf document using xournal’s highlighter, I was deeply disappointed. But, as soon as I started exploring its configuration options both those that are available from within its graphical interface and those that can be directly edited inside the config file, I realized that it was easy to greatly improve the text highlighting experience.

The rest of the document has to do with configuring xournal in such a way that it is more convenient to use it to highlight text inside PDF files. Although some of these settings can be set from within xournal’s graphical interface, I recommend editing the configuration file directly: /home/gnot/.xournal/config, since it contains more options than those available in the GUI.

The ruler exists in order to make life easier when you highlight text. It is highly recommended that you enable it for text highlighting:

startup_ruler=true

If highlighting text is your main use of xournal, then you can make it the startup tool as well.

startup_tool=highlighter

The following options make xournal’s window to start maximized and set the initial zoom to 150% respectively.

window_maximize=true
initial_zoom=150

The following options configure the highlighter. You can set the 3 pre-defined levels of thickness and which one will be the default one, set the default color and finally set the opacity (the default opacity level of 50% is just too much).

highlighter_thicknesses=2.83;8.50;19.84
highlighter_thickness=2
highlighter_color=yellow
highlighter_opacity=0.20

Conclusion

Noone said that annotating PDF files in Linux is an easy task. I have tried many open source tools for that job, but xournal seems to be the best one at the time of writing.

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Tags: PDF