Reprinting a .pdf
Because of the compression used in making the .pdf each time you “save as” or “print to” .pdf the image resolution is reduced.
I think it also depends on the image format actually used in the image that is embedded in the .pdf
.tiff does not loose quality as saved, .png is a lot less lossy than .jpg formats.
There are other ways to create a .pdf than an adobe app. I have noticed some of the Linux .pdf creators are much slower to feed to a printer. Not sure if that is due to a driver issue or if the file size is larger.
I suppose it could be that the original was extremely high resolution, which would make the file unnecessarily large, which would make it hard to download/open or e-mail on dial-up or other slow connections (i.e. in the hinterlands). Of course, that might have been the goal all along.