Ron, You're correct that you can extract a graphic image from a pdf file in which it is embedded and then save it in an image file format (WikiTree can interpret jpg, png, and gif graphic formats) in order to upload it to WikiTree as an image.
This is not absolutely necessary, however, because WikiTree is capable of handling pdf files, as well, although a bit less elegantly than it does graphic files. A recent major software modification was made and it appears that this bug (see my answer) is a new one and just needs to be fixed.