HP D7260 will not print two sided
This model printer does not have a duplex unit and therefore cannot print double sided printing automatically.
DOUBLE SIDED PRINTING USING A SINGLE SIDED PRINTER
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.