On December 31, 2017 at 14:46, mml said...
How can I post a PDF, I did a drawing of what I'm thinking about.
Convert it to a picture file, say .png or .jpg, and post it to an image hosting site. Since reddit is pretty popular, they have their own imaging site, imgur. Then (in most cases) right click on the stored image, copy the image address, and insert that into your post. Some images require some added things -- look for recent RC threads about image posting for those details.