From InDesign, you are not creating an editable PDF, but rather, one with forms fields and actions.
It is only the forms fields that you define in InDesign that a normal user can readily “edit” in any meaningful way by virtue of what is typed into those forms fields.
Further manipulation of the contents of the PDF file is possible in Acrobat Pro, but the editing is totally out of content to the original document. You can't reflow across pages or do anything particularly sophisticated (such as adding or modifying transparency) with the edit tools built into Acrobat Pro. There are some very expensive third party plug-ins that can do a bit more than Acrobat, but you must remember that for the most part, PDF is a Final Form File Format!!!
Dov is the expert in these matters, but to make it clear, you can't create a PDF form into which your user can insert JPGs photos. You can only create fields that your users can insert text, check boxes and radio buttons etc. There is a hack in which you can create a button which users can insert a PDF. Is that of interest?
I did some investigation into adding a form field to a PDF that could take a photo several years ago. Although it was possible, I abandoned the idea because there was no way to control the siz/positioning of the photo in the form field.