There might be a child record without data. You could test for that by making a GTRR button to a line items layout and put it on the invoice layout. Click it and see if a related record (line item) was made with no data. This could happen accidentally with a script.
Maybe there's something on your print layout that's hidden and causing a problem. Could be far off to the right.
In layout mode try dragging a box in the area you suspect, and go to the right (off of the visible layout space), and see if anything highlights.
Thank You Steve.
I tried those suggestions - no luck.
I think i need to pay a professional to take a peek. Any suggestions?
Can you post your db, with some sample data that shows the blank space?
I would first try to create the same layout from scratch (just the line items and one field on the main layout) and see if the problem still happens before calling in reinforcements.
Before you do that, show us a screenshot of your layout in Layout mode and/or post a clone of the file with a few sample records.