Another bit of info to this ongoing saga. The Adobe Reader software uses a PDF/a file structure. I discovered in Acrobat 8 Pro there is simple means of converting the file .... Comments>Enable for commenting in Adobe Reader... (You have to have a document open to view this) — perhaps someone can check to see if this option is available in Acrobat Standard?

This opens a dialogue warning that some functions will be lost (you lose the ability to create bookmarks/toc) but converts the document to pdf/a requirements. The end result is you can now see the missing images and also any hilites and comment symbols (although they are not interactive on the ereader). If you want to be able to view the contents of a note (made in acrobat) use the "rectangle with text" tool and it will be visible in the ereader.

If you want to to add notes again in acrobat, use the "keyboard shortcut" for creating a bookmark (as this operation is not available in any menus now) and a dialogue appears allowing you to convert back to the fully functional pdf file type.