[ag_guy]

Can you list a few?

[eviks]

Foxit, Pdf-xchange, a few others from this list

https://alternativeto.net/category/productivity/pdf-editor/

[kmoser]

I've been using Foxit Reader https://www.foxit.com/pdf-reader/ for years to mark up PDFs. The new Firefox feature seems to be a pared-down version of Foxit Reader, which seems kind of redundant to me. I would much rather have the ability to actually edit a PDF, i.e. change existing text and images.