PDF editing on MacOS is not as problematic as you might think.

• The default Preview app offers editing—you need to hit the little toolbox icon on the bar to access these extra options
• Preview does not seem to offer any functionality for dropping in images. Let’s say you need to do this, e.g. in order to robosig. To the rescue comes Formulate Pro which is a quick brew install --cask shimeike-formulatepro away
• The Preview editing is generally a bit slicker, so I would suggest using Formulate Pro as the last step, when you need to robosig a doc you filled out in Preview