Linux users probably already know all the PDF tools available from their respective repositories. Tools like pdfchain, pdfconcat, pdfgrep, pdfcrop, pdfimages, and pdfseparate seem to be the most useful commandline utilities.
However, i also use a GUI PDF editor that is typically not available via repositories. I have found this product to be invaluable and well worth mention.
Please visit https://code-industry.net/masterpdfeditor/ to make use of this extraordinary free tool.
It includes all the functions needed to graphically modify, highlight, or annotate PDFs. One of the most difficult things to do to PDFs in linux is to edit text. Be assured, Master PDF Editor will allow you to do such.