I used Inkscape a lot on PDFs with forms and broken layout. The beauty of it, you can fix other problems, too, use your own font or change the font of existing text. (:
having layering(hope that the right word for a group of text, icons and symbols) issue where icons and symbols go missing or get replaced by square boxes
Try to make sure you have all of the fonts used by the PDF installed on your system. I tend to only make small changes, but not having the correct fonts causes issues for me.