This article helps you to set up printer settings if you wish to change the default.
Go to Start Menu>Devices and Printers
Select your printer.
Right click on it and click on Printing Preferences
Under Adobe PDF page size Click on Add button
Give the Paper Name. (This is the name you will choose in Galaincha later)
Change the width to 36 inch.
Click on Ok.
Now go to Galaincha.
Click on Print Graph
Under Printer Settings, from the select option, Choose your printer.
Now Click on Change.
Under Size, Select the Paper Name you gave earlier.
Your settings will be reflected on the Paper Size now.