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.
LibreOffice Draw can make changes to PDFs.
It looks like central California foothills. Lots of current fires, especially in Socal. Cal Fire
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.