Google has removed the “first 100 pages” limitations from Google Docs PDf viewer, and you can now upload longer documents only upto 10 MB. Another change is that you can upload more than 100 PDFs, but it's not clear what's the new upper bound. The viewer is used when you upload PDF files in Google Docs or when you click on a PDF attachment in Gmail. It works by converting the pages to PNG images and it has advanced features like zoom, search and text selection. Tip: to copy text from a PDF, highlight the text and press Ctrl+C.
Source:→ Google OS