Fools and Their Foolproof Workflows --McIlroy

I can also report that from a second question looking at problems of greatest concern, it's agreed by both reports: Fonts not embedded or missing, followed closely by wrong color space and insufficient image resolution (or image missing altogether).

Until I sat down to write this, I had not realized just how closely the responses track in both reports. Given that these are two different studies conducted by two different organizations, at roughly the same time, but with different sets of respondents, the results can be considered as near-conclusive.