How to make a circuit diagram for a PDF document?
I use Irfanview to copy an image or screen save then paste crop ... edit. It supports every media format. F10 has a toolbar, It also supports all Adobe addons.  Very fast and easy after learning it.

Then paste to Open Office Writer then file> Export to PDF

But you may want scaleable vector graphics for zoom quality. However you can compress in Irfanview a 4k image down to 1%