Where I work, we accept PDFs from clients (most using InDesign) and do a conversion so their magazines are accessible via devices like the iPad. Since our software converts pages to images, all layout is preserved. Our online reader allows magazine visitors to zoom in, so page resolution has to be about 144 pixels. We have one unhappy client who insists that we've done something different with their most recent two magazines that has caused degradation in quality. I've zoomed in on an image in one of their older magazines and its most recent version in a newer edition, and confirmed that the recent version looks pixelated and has excessive contrast/saturation. However, 1) None of our other clients have this problem despite their magazines being run through the same software, and 2) the settings inside our software have not been changed in more than a year.
I figure I have two options. Either look at the PDFs they sent us and figure out what they're doing wrong (their graphic designer has limited experience) or find a spec sheet somewhere that lists the best InDesign PDF output settings to use for Web reading (including retina screens), and send those settings to their designer.
Problem is, I don't know how to analyze a PDF, and my search for the optimum InDesign output settings leads me down several different roads. Can't really test it myself because we rarely use InDesign at our end. Suggestions?
Why not run a preflight check in Acrobat Pro? You can set up a check for images of less than x ppi.
I'll try that and report back if I encounter any problems.