Inkscape is a superb vector graphics editor which supports a variety of formats. Unlike Inkscape, you can't use snapping at all, so the positioning precision can only be perceptual. For instance, I find it convenient to use Vim's CTRL-X and CTRL-A commands to respectively decrease and increase values as with a slider and :w | !latexmk -pdf short-cut to to save and compile the file quickly.

You'll soon want to use all the shortcuts you can wield to make this bearably fast. This will involve repeatedly changing coordinates and checking the result. This approach being non-graphical, the difficulty lies in actually finding the right position for those nodes.

This part is relatively easy and can be automated on the fly with any good text editor. The idea is to make an overlaid tikzpicture for each page and place e.g. text nodes.

The L A T EX graphicx package supports PDF perfectly and Ti kZ is a rather good solution for placing text and adding drawings. This approach doesn't allow you to change the PDF per se, so much as it lets you add contents on top of an existing PDF file and generate a new PDF. I quite like using L A T EX myself or Inkscape, depending on the needs. Googling for pdf editor linux will take you to discussions such as Which programs can I use to edit PDF files? or How to Edit PDFs? which will refer to tools such as flpsed, PDFedit, even LibreOffice Draw. Two ways of editing existing PDF documents: one with LaTeX for automation's sake, another one with Inkscape for visualisation's sake.

How to use inkscape to edit pdf file