The problem is not with Word and there is no need to switch to Adobe. The Adobe writing program has to be purchased and would not resolve your problem.
The Photo image you take of the signed/sealed document is where the problem occurs.
There could be a variety of reasons but most likely your computer is creating the photo image in a default setting (like Nero, for instance) and it cannot be opened by those who don't have that program, thus the suggestion to create the images in bitmap.
However, if you are a bit savy with the puter, as you seem to be, simply change your default program for Jpegs to a Microsoft program like Windows picture and fax viewer or Windows Live Photo Gallery and the problem should be resolved for those receiving your scans.