How can I prevent Excel from adding page breaks??

One idea is VBA:
ActiveSheet.DisplayAutomaticPageBreaks = False

but note that it is sheet specific. You might want to loop through all sheets, such as
for each ws in worksheets

but even that is imperfect because you may add more sheets and you also have to remember to run it whenever you create or open workbooks. Nonetheless maybe it will at least be less work for you to go Alt-a and get all sheets in the active workbook (or all open workbooks) via a UDF, vs. manually clicking the option every time. Further timesaving might be achieved by putting that into App_NewWorkbook and App_WorkbookOpen; if I'm not mistaken, then you might almost not have to go into the option ever. (Edit: Adding a worksheet may require manual action. I can't remember if there is an event for sheets.add . You also might want to determine if copying sheets preserves the setting.)