I'm not bitching about the quality (unless they're technical drawings, then they better be the best possible. Some of those drawing are so bad to begin with, adding artifacts to make it worse is a no go). I'm wondering about the technical aspects of the pdf itself and why there are artifacts.
I've been meaning to get a PDF creator of some kind, but I've never had any inclination to convert any of my scanned books or manuals to pdf yet. For instance, I would love to get a better quality copy of my Sega CD manual instead of the crap photocopy Sega sent me so many years ago.
No problem I got ya!
This one inside was not too bad since it was line art some with actual photos it can get dicey when you try to make it a manageable size for the web its a bandwith killer to have alot of large size .pdf files.
I have lots of other .pdf on my site just on other topics (I kinda became the home for alot of orphan files LOL) and some are horrible scans and so bad pdf.
I use Adobe Acrobat to make my pdf files and you can just drag and drop the images into Adobe and save as a pdf or you can highlight them and print them into Adobe's distiller and it will change the settings to suite what you are creating say a E-Book.
It will rotate and crop and adjust DPI but you have to watch it sometimes it does odd things.
If the manual is not in color just scan the file in grayscale (or color and then convert it to grayscale) this will reduce the size of the file quite a bit. You can reduce the file to true b/w (2 color) and it will be even smaller BUT you lose alot of quality in most cases that is where you get those horrible scans of old manuals and such.
The wiring diagrams in this one were 2-3 pages wide so I scanned them overlapping and mated them together and then adjusted the scale so they would be legible but fit in a 8.5 x 11 size.
The artifacts you see are from 90% compression of the jpg file to try and get the size down to 4mb the larger is about 6mb and is compressed at 60%.
They were scanned full size and then a copy was compressed and used for the pdf the ones with less compression do not have the artifacts so if you wanted to save them for posterity you would be happy with the results I think.
For the web well we have to make sacrifices.

Hope that helps to explain it a little better maybe
