Create a custom page size.

Way described below is alternative and to be used only in exceptional cases.
Follow this link to find out how to create a custom page size default way:
ImagePrinter Pro – Basics

Windows 7 and Later

• Start the Control Panel > System and Security > Administrative Tools
• Open Print Management
• Open – computer name
• Click on Action menu Manage Forms…

• Click Create a new form
• Define width and height
• Click OK

Create new page fom for Windows 10:

• Start the ControlPanel/All Control Panel Items \Administrative Tools
• Open Printer Management
• Or Open Run by Windows+R, type printmanagement.msc and tap OK.

Please note that Printer Management is not present in Windows Home editions

• Open Print Server
• Right click Forms and choose Manage Forms… in context menu

• Specify new forms parameters and press Ok