How do I remove the paper from a paper jam in the HP Photosmart C4780

You can clear paper jams by checking three places: 1. Open the front door and wait for the cartridges to move. Then, move them carefully with your hands and look for jammed paper. 2. Remove paper from the input tray and look for jammed paper (you may need to lower your head and see straight into the input tray for that) 3. Open the back door and look for jammed paper. Most HP printers have a back door (used by the optional duplexer unit) that you can open and look for jammed paper.
If you can't find it, then you might need to dismantle the printer in order to clear the jam.

Here is a link to a detailed description from HP.
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01673676&tmp_track_link=ot_faqs/top_issues/en_us/c01673676/loc:4&lc=en&dlc=en&cc=us&product=3794615