Since mobile ADE reflows PDFs one page at a time, I think you would need to modify every page to stop reflow entirely. I suggest trying something like adding a box around the text (i.e. a page border), or add an image-based header and footer that ADE can't handle (you would have to experiment to find one), or a watermark.
Alternatively, there are tools for converting PDFs to images. One is
PDFRead, which is sticky in the workshop forum (probably because it does not seem to have PDF output).