Adobe released Acrobat 6 today, including a new version of the free Acrobat Reader. Download Acrobat Reader 6 here. Acrobat PDF format is starting to be used everywhere – you might as well have this upgrade in case you want to view multimedia content embedded in a PDF file or simply use the improved interface.
Incidentally, I don’t like “download managers.” They tend to be unhelpful bits of spyware, reporting information back to third parties without making my life any better in return. I don’t know much about Adobe Download Manager but I turn it off on general principles. Watch for the checkbox on the download page.