Adobe is trying to make sure that there is Adobe PDF reader in every popular systems. You can find Adobe PDF Reader for Windows, Mac, Linux, Palm, and also for Symbian. From my opinion, this is not the best PDF reader out there. I only use this application to read small PDF files or for making sure I have downloaded the correct file from the internet.
If you intend to read large PDF files, it might be better for you to just convert your PDF files to Mobipocket format, or even HTML format.
Adobe Acrobat Reader is only available for Nokia 6680, and can be downloaded from adobe.com