Add Custom Paper Size in Windows 10

To define a new custom page size, follow these steps:

1. Type Printer & Scanners in the search box in the bottom left corner of your screen, then click to select the option Printer & Scanners.
2. Click a printer in the list (e.g. Plotter_401_z3200), then click “Manage”.
3. In the dialog box that appears, click “Printing Preferences”.  On the “Paper/Quality” tab, under “Print Quality”, select “Custom Options”. Under “Paper Options”, select “Custom” and enter the appropriate width and height.  Be sure to set your width smaller than your length.
4. Give the new page size a unique and descriptive name, such as ’24×36′ or ‘Custom A size’.
5. Click the Save button.
6. Click the OK button when finished.

This new size should be available for you to use on all similar printers. One note on this, when you do the first step, you likely will not see all of the printers listed. This is due to Windows 10 grouping them together. Simply pick a printer from the list that is similar to what you intend to print to.

Add Custom Paper size in MacOS

1. In any application go to File -> Page Setup
2. Under Paper Size choose Manage Custom Sizes
3. Click the + to create a new size. It will be called Untitled
4. Double click the name Untitled to set a name you want
5. Set the width and length options and click OK

You will now see this custom size in all your applications (relaunch of each app may be needed) as an available paper size.