PDF reader is a Office Tools software developed by PC-Gizmos. After our trial and test, the software is proved to be official, secure and free. Here is the official description for PDF reader:

Edit By BS Editor: PDF Reader is a freeware enabling you to read and edit PDF and most office docs online, in Google docs, from your browser.
After installation, links to PDFs and docs would simply open online, quickly and risk free.

PDF reader will automatically fetch gPDF from userscripts.org and run it using the pc-gizmos framework.