For a while now I have been fighting with Acrobat, printer settings and Word to try and figure out why when I converted some document to PDF their pagination was changed (ie: if the document was originally 110 pages enough small formatting changes would be made to turn the PDF into a 112 page document). 

Apparently this has to do with the way Word reads a document and your default printer.  When you first open a document in MS Word it flows the text in the document according to your default printer's setting (for example, margins).  If your default printer is not the Acrobat Distiller it won't flow the text according to the settings of the Distiller and thats where you start having problems.  Below is a copy of the techdoc an Adobe Expert sent to me detailing a few ways to handle this problem in Word as well as a solution for WordPerfect users:

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Technician comments:

end technician comments.
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Adobe Systems  Technical Document 329296
Title: Text reflows into more or fewer pages when you convert a file to PDF
(Windows)

Issue
An Adobe PDF document has a different text layout and number of pages than
the document from which it was created.

Solutions
Do one or more of the following:

Solution 1: If you converted a Microsoft Word document to PDF, adjust the
document in Word.
You can adjust the document by forcing Word to reflow the text, lowering
the print quality, enabling Word to use printer metrics, or using the
Shrink to Fit option. After you adjust the Word document, re-create the PDF
document. You may need to try several of these procedures to get the
results you want.

-- Force Word to reflow the document:
   1.       Open the original Word document.
   2.       Click File > Print.
   3.       Choose either Acrobat Distiller or Adobe PDF printer, and then
      click Close or Cancel.
   4.       Select File > Page Setup
   5.       Click OK on Page Setup without making any changes. Word reflows
      the document.
   6.       Fix the formatting (for example, line endings, spacing, section
      breaks).

-- Lower the print quality to 600 dpi (dots per inch):

Note: Any images with a resolution greater than 600 dpi will be
downsampled.

   1. Make a backup copy of the original document. (If you need to print
      the original document to a printer, use the backup copy, which is
      already formatted for a printer.)
   2. Set Adobe PDF printer or Acrobat Distiller as the default printer.
      For instructions, see "Background information."
   3. Change print quality to 600 dpi in Adobe PDF printer or Acrobat
      Distiller. For instructions, see the documentation included with
      Windows.
   4.       Open the document, and adjust the layout as desired. For
      example, change the font, font size, margins, or spacing.
   5. Re-create the PDF document.

-- Enable the option "Use printer metrics to lay out document" in Word.
   1. Set Adobe PDF printer or Acrobat Distiller as the default printer.
      For instructions, see Background information.
   2.       In Word choose Tools > Options.
   3.       In the Compatibility tab, select Use printer metrics to lay out
      document, and then click OK. The Use Printer Metrics to Lay Out
      Document option in Word shows how the document layout will appear
      when printed to the default printer.
   4.       Adjust the document layout so that it appears as desired. For
      example, change the font, font size, margins, or spacing.
   5. Re-create the PDF file.

-- If the PDF document has an extra page, choose File > Print Preview in
   Word, and then click Shrink to Fit. Then, re-create the PDF file. For
   more information about Word's Shrink to Fit feature, see the Word online
   Help.

Solution 2: If you created the PDF document from a WordPerfect document,
adjust the text flow in WordPerfect.
Open the original document in WordPerfect, and then choose Format > Make It
Fit. WordPerfect forces the document to fit on a specific number of pages,
but it may still reflow text to a different page. For example, if the last
page of a WordPerfect document has only a small amount of text, WordPerfect
may reflow text forward from previous pages as far as the bottom of that
page.

Solution 3: Reformat the text in the original document with a different
font.
If you use the Adobe PDF printer, use a Type 1 font. Keep in mind that text
formatted with a different font will probably flow differently than text
formatted with the original font.

Background information
When you create a document, the page layout options and available fonts are
determined by the default printer driver or by the target printer driver
selected in the application. Changing to a different printer driver affects
how text appears and prints in a document. If the original document wasn't
created with Adobe PDF printer or Acrobat Distiller as the default printer,
the text in any PDF document you create can reflow unexpectedly. Reducing
the print quality to 600 dpi ensures that the original document won't
reflow when it's converted to PDF.

To set Adobe PDF printer or Acrobat Distiller as the default printer:
1. Choose Start > Settings > Printers (Windows 2000, Me, NT, 98, or 95) or
   Start > Printers and Faxes (Windows XP).
2. Right-click Adobe PDF or Acrobat Distiller, and choose Set As Default
   Printer from the pop-up menu.

Note: In Windows XP, Set As Default Printer isn't available if Adobe PDF or
Acrobat Distiller is already the default printer.

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