Inserting an image in a PDF is part of Editing which wont be possible using free Adobe Acrobat Reader DC. You will require Acrobat application Download Adobe Acrobat free trial | Acrobat Pro DC to achieve this goal Acrobat Help | Editing PDFs.
I don't know if this is still a problem, but I've come up with a simple solution.
Copy the image you want to paste to clipboard (right-click "copy image" on internet or use Microsoft "snipping tool" - "edit" - "copy")
Open the "comment" toolbar in Adobe Reader and select the "add stamp" tool. Select the last item titled "Paste Clipboard Image as Stamp Tool
This was done using Adobe Reader 2017
This worked for me thank you
It worked for me also. Thank you very much 🙂
Thank you so much. It worked.
This was very helpful. Thanks
Thank you...Worked great on my Mac... I opened the image in previewer then edit - copy and then was able to paste from the clipboard using free Adobe Reader DC