First check it these numbers appear in the text only view in the PDFView. If yes, send me one sample of these PDFs and I try to create the regular expression to extract the bates numbers to a custom field.
Another way to do it is to export the PDFE grid (File>ExportGridFields) containing the files where you want to add the bates numbers to a csv file (create first a grid layout with the custom fields where you are going to enter the numbers), next you need to edit the csv file in a spreadsheet editor, MS Excel for example. In here you have to construct a function to automatically add the numbers to these empty custom fields, producing equal numbers, to same files, you already added to the pages with Acrobat. After csv file edited you can import it again into PDFE database (File>Import...).
Even so, the first solution, if possible, it's a better one.
Also, is there any way to break out the number of pages in a document? I noticed that Acrobat also assigns the "MailAttachment" tag to mail attachments...
Are you referring to the number of pages of the pdf document? If yes, that number is already available, you just need to create a custom grid layout to include that column and this way show it in the grid.