Maximum File Size and Pixels for Uploaded Business Documents

I am creating a php form that accepts an upload of business documents in a variety of formats .pdf, .doc, .tiff, .jpeg, etc. and I need to restrict the size of the files that are uploaded. It's trivial for me to restrict the file size, but I'm not sure if I should also restrict the max height/width, which are also available options.

I will need to occasionally print these documents to 8.5 X 11in开发者_Python百科ch paper and have them be legible, but don't really care if images come out. Should I restrict the pixels sizes or is that redundant with restricting the file size? If so, do you guys have a recommendations for max height/width for, say, a 5MB file size limit? I really have no idea what the relationship between pixel size and image size is or what the common pixel sizes are for scanned images.

Also, what would be a reasonable size expectation for a legible print per page?

8.5 X 11 inch with 300 dpi => 2550 x 3300 px (or 3300 x 2550 px). But i'm not sure that's usefull to check sizes: how to know if the user want an hight resolution?