For the print format of a document, you can set default Print Format in the Customize Form.
For the report, it is not configurable for now. Check the script of General Ledger print format for the reference on how to do it. Will be great if it could be done from the UI itself, and your contribution on that front will be highly appreciated.
Yup, we have no trouble with creating custom print formats for Documents. We’ve also created print formats for reports… but we want to study how frappe/erpnext’s default print format is rendered since we like how it looks and we’d like to look at how the report data is being formatted. Which is why I’m trying to look for the the html template for the default report print format.
But thanks for the info @umair. I’ll look into it.