This is a really bizarre one:

When I print a particular spreadsheet, Excel (2003) for some reason breaks
the document up into multiple files instead of just the one document as you
would expect.

Instead of one 12-page document I end up with:
File 1: Pages 1-3
File 2: Pages 4-6
File 3: Pages 7-9
File 4: Pages 9-12

This doesn't matter when printing hardcopy but when printing to PDF it's
really annoying. I can't figure out why it would do this! Any ideas?

Troubleshooting tried:
- it's definitely Excel and not the PDF printer - I've tried printing a
paper printer and the printer log shows that multiple files were sent.
- it happens whether I select all the worksheets and print "active sheets"
or whether I just select "entire workbook".