Prepare proof exports, not raw camera originals
Use reasonably sized proof images that represent the intended crop and tone. Keep RAW files and high-resolution masters separate from the selection PDF.
Use filenames as selection IDs
The simplest client workflow is usually 'send back the filenames you want.' A proof sheet makes those identifiers visible next to each image.
Add a visible proof watermark only when needed
If a job requires a visible proof mark, create the marked derivative first. Do not overwrite the unwatermarked master just to build the selection sheet.
Do not confuse a proof sheet with color proofing
A PDF on an unknown display cannot guarantee color-managed print output. Treat it as a selection/reference document unless your full workflow is calibrated.