You haven't given much to go on.
Someone more knowledgeable than I would know what a Crystal Report is, and VB.net. Does this imply special formatting of charts or tables, or is it essentially a text document? If the document itself allows, it's possible that something hidden in the formatting is reducing it, unless, by some chance, you have Track Changes on, which might would reduce your entire page size in order to provide the wide right margin for comments or other changes.

I would suggest creating a copy of the document. Then open it, select all (Ctrl+A), click on "Clear formatting" in the Styles pane or press Ctrl+Spacebar and Ctrl+Q, to remove all paragraph and character formatting. Reformat if necessary, and then see if it prints properly. If it's a large document, you might, in the copy document, delete everything except the first 5 or 10 pages, then follow the above steps, and see if you're successful.

Does this solve your problem?