Foxit PDF Reader
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Full user review
"MUCH BETTER THAN ACRO READER"
Loads very quickly.
Does the same basic job.
You can highlight bits, add stickynotes, type stuff (usefull for pdf forms) and other things. These extras leave a message on the saved copy but it's sensibly placed so it probably won't obliterate anything.
It's well worth paying for but you don't have to.
Not enough people know about it and I get asked to deal with their Acro Reader issues.