PDF Software Suggestions

Hello,

Curious if anyone has any suggestions regarding software for PDF manipulation {viewing, creating, editing, signing} that are available on Linux. Preferably Universal packages, but not a requirement. Any non-mainstream apps are definitely welcome here.

I use masterpdf (non-free, proprietary) at work, https://code-industry.net/masterpdfeditor/. Mainly for form-filling and signatures. There is also pdfstudio https://www.qoppa.com/pdfstudio/ although I have not used it. xournal/xpurnal++ is good for annotation (open source) and works on laptops with touch screens as well.