After allowing people to collaborate on documents, spreadsheets and presentations, Google Docs will support a new file type: PDF. Judging from Google's code, PDFs will have a distinct section and won't be imported as Google Docs documents.
An icon for PDFs has been available for a while and when you visit http://docs.google.com/#pdfs, Google Docs informs you that there are no PDFs in the list of documents.
Google has a pretty good PDF viewer in Google Book Search and Google Patent Search, so I expect to see some limited editing features added to the PDF viewer before repackaging it as a Google Docs application. Fortunately for Google, no other competing services provide a decent online PDF editor.
"Since becoming one of the original Gmail and Google Docs users way back in the beta-beta days, it has been a continuing source of confusion and irritation to me that we STILL can't even upload PDFs to Google Docs. (...) For those of us with laptops and iPhones it would rock to offload as much as possible onto the web and having sharing capabilities with our clients and colleagues for ALL our docs, not just a select few. In the professional, business, and government communities, PDFs are the transmission document of choice," commented JAVA4DIVA in a thread from Google Docs group.
Update: In less than a day, the feature has been added and you can now upload PDF files, share them and view them online. The PDF viewer is not very advanced, but you can use it to search inside a PDF file, select a block of text (Ctrl+C to copy the text) and go to a certain page.
10 minutes ago