How to set page defaults in zoho writer?

How to set page defaults in zoho writer?

hi,

everytime i open the zoho writer i have to change the default page settings to - A4 from letter, margins to narrow and header and footer to 0. I cannot set this as default as that option is grayed out! so I am unable to click it. I saved the document and tried, still that option is grayed out. attached screenshot.