How To: Print an ArcMap layout to an exact scale - 9.x
Instructions provided describe how to set the ArcMap layout to print at an exact scale.
Navigate to View > Layout view.
Verify that the map scale is set as desired. If it is not, enter the desired map scale either in the map scale combo box or in the Data Frame Properties dialog box Data Frame tab. See the ArcGIS Desktop Help topic 'Setting the map scale' for more information.
To lock the scale, right-click on the Data Frame and select Properties. Click on the Data Frame tab, click the Fixed Scale radio button, and click OK.
Navigate to File > Page and Print Setup. Set printer and paper size as desired. Make sure that 'Scale Map Elements proportionally to changes in Page Size' is not checked.
Click on the 'Use Printer Paper Settings' checkbox. See note in step 7 if this setting can not be selected.
Navigate to File > Print. Set the Printer Engine and properties as desired.
Note: If 'Use Printer Paper Settings' can not be selected in step 5 for some reason, select 'Tile Map to Printer Paper', even if there is only one tile. The other option, 'Scale Map to fit Printer Paper', scales the map layout and invalidates the map scale.
See the links in the Related Information section below for more information on best practices for Page and Print Setup and setting a custom printer paper size.