How to print on both sides of the paper in canon lbp2900?

Plenty of places to look at as you give me no clues! Is the power light on? If not check the power lead and power point. Is the toner OK? Is the paper OK and the paper feed working? Does your computer show it is linked to the printer?
You can do troubleshooting at the Canon website
http://www.canon-europe.com/Support/Consumer_Products/products/printers/Laser/i-SENSYS_LBP2900.aspx

>> Check the paper jam
>> Remove print cartridge
>> Clean the sorroundings
>> Check the printer door and also check the door sensor (which is located at left side of print door.

>> It may help.

print there was a black mark at the full paper

If your printer does not have a duplex unit then the printercannot print double sided pages automatically.
You can print double sided pages but you have to do it one page at a time.
First print Page 1 then place the page back into the paper tray, but turn thepage upside down and the print Page 2.
Then print page 3 on one side then page 4 on the other side and repeat for therest of the document.
I suggest you try a test page first, to get the printing the right way up onboth sides of the page so it reads correctly.

To print both side automatically you need a hardware called Duplexer. Cannon Laser Shot LBP-2900 dont support Duplexer. You need to manually turn the paper everytime.

Regards,
Shrey

Do a hard reset of printer to see if that clears up the electronics memory and restores operation. If that procedure and reinstallation of software does not remedy situation then something is wrong with the printer.

how can i get the number of printed copies in canon lbp2900

I take it you are using windows,
Open control panel, open printers and faxes, right click on your printer icon.

Left click on properties, left click on printer preferences, left click on page setup, down near the bottom there is a box called duplex printing, tick that and you are on the way.....

I have a same problem .... somebody help us. :(