i have the same requirement from my user / customer side. They want to be able to put text and images in a text field and at the end there should be an PDF Export of these information.
I have realized this by using the rich text editor of mendix and then creating a document template using dynamic label and conversion to PDF.
In the beginning it seemed to work. To show or enable storage of images you should set the sanitize option of the rich text editor to no. Otherwise the picture will be deleted.
But the problem in my case is that by disabling the sanitize option the rich text editor is generating code different in XHTML. This leads in my case to a failure at the conversion to PDF.
I think your problem can be solved when you disable the sanitize option in the rich text editor but be aware that you perhaps then got other reactions.