Is the PDFViewer-0.03 in zip format? If so then just unzip and it will be something like this ... PDFViewer.app. Then just drang and drop the PDFViewer.app folder using iPhonebrowser to the /Applications folder.

One thing about iPhoneBrowser is dat u cant set the permission to the files or folder, not like WinSCP (which need u to be in a wireless environment also). If the author didn't set it properly then u can execute the app. But just try and see.

Hope that helps.