There we have it: A commercial program for editing PDF files that is not as expensive as Adobe’s Acrobat and is available not only for Windows and OS X, but also for Linux. Moreover, the Linux version of Master PDF Editor is available free of charge for private use with a limited feature set; this will get you quite far. If you want more, you have to unlock the paid features.
Master PDF Editor is available in two versions. The version for newer 64-bit operating systems uses qt5 as graphics library, the version for older operating systems is based on qt4 and is also available in 32-bit.
On the download page of the manufacturer you can find deb packages for 32 and 64 bit, which can be easily installed after downloading:
sudo dpkg -i master-pdf-editor-*.deb
In the Open Source department, there is of course Ghostscript, a comprehensive command line tool including an API for PDF and Postscript, but the available GUI programs are outdated and rudimentary. A full-blown, up-to-date open source PDF editor is not available. Or maybe there is: Even though LibreOffice is not a PDF specialist, it can be used to edit PDFs by opening them in Draw. New documents may be created in Writer and then exported as a PDF. Individual PDF pages can also be edited in Inkscape.