Recently i had a malware which is located in a PDF file. PDF files are important part of most computer users life. When something goes popular you could see some special malwares for them prepared already. So i believe we need to carefull about pdf files.
On the other hand, the slow operation speeds of Adobe reader (that is because it's plugins i believe) make users to choose other pdf readers. If you got a competetor like Adobe you need a support, generally pdf readers get this support from somewhere like ask.com via toolbars while their setup. And this toolbars can track your online activities etc...
But not all users carefull about this issue and they setup rule is pressing always next untill they see finish button.
There are some softwares ( foxit, pdf-xchange, some others i don't know) which have these kind of toolbars.
So i would like to hear from you, your opinions and your choices for pdf reader.