Do I place the paper face up or down when faxing from a HP 6210xi

on my fax machine, hp brand, the item is placed in face down.
this should apply to other brands.

If it is on the table top then face down. If you are doing it through the auto feed then face up.

Face-up!

You place the paper face side up when feeding through the loader on top. You can also scan the fax in placing the paper face side down on the glass plate of the scanner portion.

The paper should be up facing while using a fax.

Should be a drawing on the paper tray, most go face down. Try a copy first to see which side copies and which side gives blanks.

Your manual can be found here: "http://h10025.www1.hp.com/ewfrf/wc/manualCategory?product=424230&lc=en&cc=us&dlc=en&lang=en&cc=us"

The simple answer is face down.

Look at the input tray it shows a symbol of an original.

If the lines on the symbol face you , then put the paper in face UP.
If the lines are on the folded corner of the symbol, then place the paper in face DOWN.

If you are still not sure, place the paper in face UP and press "COPY"
If it copies the page, then that is the correct orientation.

If thre copy is blank, repeat the copy test with the document face DOWN.

is your printer is copying from scanner

Most faxes are face down. check the symbol on the paper input, there is a symbol of a paper with the left corner bent. This means face down