Hello,
I have done a pretty grid I want to print but I don’t want to print “cells indexes” ( first column with numbers and first line with letters ).
To turn on/off gridlines or row/column headers, you’ll need to go into the Page Formatting dialog.
Go to: Format → Page, then go to the “Sheet” tab. Under the “Print” heading, make sure that the box is checked for “Grid”, and unchecked for “Column and row headers”.
some minutes faster than me 
… took some time to upload the screenshots…
To enable printing the grid just for the current sheet, select Menu “Format” → “Page…” and select the “grid” option:
If you want to activate this option permanently, you should modify the page style. To do this, select Menu “Format” again, then “Styles and Formatting”, or hit F11. A window showing the available styles will appear:
Select the second button at top to select the page styles. To modify the “Default” page style, right-click the “Default” entry, select “Modify…” from the context menu. You will see the same dialogue as displayed above.