Currently I'm working on a lighter(and hopefuly better) revision of PDFViewer 0.3 by James Milne and NerveGas. you can find it at :
http://code.google.com/p/solena/
right now it's in beta stage and very usable (at least for my needs).
Improvements :- Supports navigation by page number (little book icon on the navigation bar)
- Supports landscape
- Integration with mobile finder (Double tap on PDF files would open them with Solena)
- Remembers most recently used PDF settings (open last pdf file from last page number,offset and zoom)
- Supports opening of large files
- Some little improvements

Sorry about the unfriendly way of installation, specially integration with mobile finder.Please note that double tapping on pdf files in MobileFinder is currently the only way to open a pdf file.
also note that tapping on Solena icon on springboard would open the most recently used pdf file from the last page with last configurations. it mean's if you didn't open anything yet,the application will immediately close.