If you are printing a tiled pattern at 100% (actual size), using auto portrait/landscape, the 7.5 '' x 10'' tile should be centered on your Letter Size or A4 paper sheet, with a 1/2'' margin all around.
If the printer is using margins that are too wide, truncating the tile in the process, it might be because of incomplete Page Setup information. When it's missing information, Acrobat uses default margins that most of the time results is more white space along the edge than what your printer can do.
In the window where you select the print options, click on Page Setup and make sure "format for" is set to the printer you are using. See the difference in margins between "any printer" and a specific printer:
With the specific printer, the margins are smaller and the edge of the tile is no longer truncated: