Manual feed how do I manually feed paper into my HP photosmart 3310? I'm trying to print on invitation vellum but it is too thin

Try placing some standard paper behind the vellum paper, it might assist in holding correctly while printing.
Being so thin the paper I would guess is folding up under the print head? if so look through all the printer properties, under the maintenance section there may be a "set Plattern Gap" (set to wide) or "Thick Paper Setting"
Selecting these raises the print head up to allow for thicker paper to pass through, but can also help thinner paper from folding up under the heads.
I hope one of these works for you.
Regards GM

Go to this link and look for your answer Techbelkin

Black printer ink in HP Photosmart may fail to be recognized by the printer. Most times an error message will be sent indicating that something is wrong with the black print cartridge. Sometimes the printer may accept to print with the black ink, but the printouts may have horizontal lines and very illegible letters. In such a case a manual cleaning of the print head should be carried out. In doing the manual cleaning, one should spray Windex heavily on paper towel and wipe off the surface of the print head.

http://www.retrevo.com/support/HP-3310-Multifunction-Printers-manual/id/260ci562/t/2/
http://www.fixyourownprinter.com/forums/inkjet/39471
http://personafile.com/Hewlett-Packard-HP-Photosmart-All-In-One-Printer-Copier-Scanner-Fax-3310-Q5863A%23ABA-829160970424.htm

use the manual feed tray, and set the paper type from the printer driver

Make sure you have up to date drivers installed for this printe, if not you need to go to the HP website and download them. Also there are two places you need to change the paper size, in the document page setup as well as select correct paper size in printer settings. Hope this helps.

1. Turn the printer off and open the access cover.
2. Look for any obstructions in the paper path and remove them if necessary. (It is possible to move the carrier assembly with the power off.)
3. Turn the printer on, load some paper, and press the Form Feed button.
4. Watch the paper as it feeds through and try to determine where the jam is occurring.
5. Check to see if all the rollers are turning.

If all the rollers are turning, there may be something in the feed path that you can't see. Go to step 6.
If not, there is probably a feed motor or a gear problem and the printer may require service.
6. If the paper is jamming under the carrier assembly, you may be able to fix it using the manual feed slot.
7. Turn the printer off.
8. Take a #10 envelope and feed it through the left side of the manual feed slot until it comes right through the printer to the back of the exit rollers.
9. Move it up and down first, and then slowly move it over to the right side. If something is stuck under the black guide plate, this may work it loose.

Don't know if this will help but. I had a HP printer that would not feed the really heavy weight photo paper, I just backed down a couple weights and it worked fine...

Ran into the same problem. The problem is that the printer's paper sensor sees through the vellum and therefore doesn't think any paper moved into the print position. To use vellum, fold up 1/4" edge on a standard peice of print paper and place the leading edge of the vellum under the flap. Place the paper and vellum into the printer and print. The printer will pull in the paper and the vellum together. Make the paper fold tight and straight to prevent jamming. You will need to feed one sheet at a time. Also the Epson inks take a long time to dry on vellum. I let mine dry overnight.

you can get the manual, by entering a model number through the printer driver link here