When you are viewing the report in design mode, does the little square at the top left corner have a green triangle in it? If yes, there is a problem and Access will tell you what is. In this case, I would expect it to say something like "your report is wider than the printable space. This may cause blank pages."
Look at the report in print preview and then switch back to the design view and try to indentify which lines are too long. Adjust their length and repeat until no lines appear on the blank page. Then, grab the right edge of the report in design view and drag it leftward as far as it will go.
If you are still having problems after the above, there maybe some coding drawing the lines so have a read through the VBA for the report.
To answer the original question:
Is there a way to force all elements of the report, including graphics, to be a speficied width?
If everything in the report is a full width item (text boxes, lines etc) you can click in the ruller at the top of report to select everything and then set the left position and width to whatever suits.
For example, if the printable width is set to 6.5" as suggested by Statsman then set left as 0 and width as 6.5 (or mayb 6.49 to make sure).
Hope this helps