Thanks for contributing to The Manual Project!
I always verify the DPI for accuracy whenever a new contributor submits their first work. With pdf's it's a bit harder since I can't get at the raw images without extracting them first, but I can still eyeball it in Acrobat.
If you're able, I encourage everyone to upload their work as zipped images so that everyone can view them in their browser without needing a pdf viewer.
Thanks for pointing out the Final Fight 2 entry, I'll clean that up.