If you need a PDF reader for Nokia N97, Acrobat Reader LE is one of the best but will have to pay for it after the trial period. But there really free reader for PDF files. This can be found on http://view.samurajdata.se

This is an online viewer, with which you can view PDF and PostScript files as browsable images and Word documents as web pages. Given a URL on the net or a file on your computer, the viewer will try to retrieve the document, convert it and show it to you. No plugin software is required.