Images - multiple for use in Quotes/invoice

At the moment I can only use 1 company logo but our company has a number of brands and for quoting/invoices, I want to be able to use templates with different images.

How do I add a new image to a pdf template. The WSIWYG is not very good in that you have to put a URL in instead of being able to upload a new image - not sure what URL I need to use as have put an image into the Upload folder via FTP but can’t seem to work out a path.

Should be as easy as what I can do in the WSIWYG in Joomla using JCE.