PDF is the envelope, not a miracle
One photo, one page
A single still becomes a single PDF page. That is enough for a signed form. A chapter of a workbook wants the multi-page flow so the reader flips instead of unzipping.
Order is a choice you make
We will not guess that page 2 is the back of page 1. Add captures in the sequence a human should read them.
Size after export
A 12-megapixel phone can make a “one page” PDF that email hates. Compress after you like the crop — do not crush first and then wonder why type is mush.