"I have a document footer with text on the left side and page # on the right." Do you mean the left side and right side of the same page, or different footers on odd and even pages?

I work with other people's documents, and sometimes I get results that yield a 'hidden' footer from an old report that doesn't display or print but is nonetheless embedded in old information. I have Office 2010 for Windows at work. I'm not sure what version you have or whether the controls for footers appear any different. But from my perspective I'd suggest:

1) you select "Show" (the paragraph symbol on the home ribbon) to see all the formatting marks, etc.

2) you see once you click into the footer area whether there are a bunch of section breaks with different footers for each, or at least some, sections, causing one page to have the footer and the next or previous to not have it.

3) You look on the Design tab which should display in the ribbon when you're actually in the footer real estate on-screen... and see if "Different First Page" is checked, also if "Different Odd & Even Pages" is checked. To find my hidden footer, I tend to uncheck the Different Odd and Even thing, then it shows up on the next page and I can then remove it more readily.

4) Also, with the format characters displayed, and also making sure you're in View/Print Layout viewing, you can see if for some reason there are bunch of line or paragraph breaks pushing the footer off the visible portion of the pane.