Creating a custom page number
The Page Number tab on the Map Sheet Properties dialog box allows to you set map sheet numbering by one of two methods: Use Map Series Page Number Option or User Specified.
The User Specified option allows you to type the page number of your choice in the User Specified text box.
Steps:
- Start ArcMap.
- On the main menu, click Customize > Toolbars > MPS Atlas.
- Click the MPS Atlas window button  on the MPS Atlas toolbar. on the MPS Atlas toolbar.The MPS Atlas window appears. 
- 
Right-click a shared or single map sheet and click Map Sheet Properties.
The Map Sheet Properties dialog box appears. 
- 
Click the Page Number tab if necessary.
The Page Number tab appears.  
- 
Click the User Specified option.
- 
Type the page number you want to use for the map sheet in the User Specified text box.
 Note: Note:Page numbers can be integers or strings. 
- Click OK.
6/14/2012