Enable printing functionality for custom button on customer portal

Hi Community,

I have a custom section, I added a custom button on edit view and button is visible on CRM and Customer portal as well.

On CRM that button is functional and on click the pdf is successfully downloading.

But on Customer portal that button is only visible and on click the pdf is not downloading.

from this post ( https://community.bpmonline.com/articles/how-show-printables-print-butt…) I come to know that I need to apply some permissions to enable OOB printable functionality for customer portal. I tried to apply all from this post but that button is still not functional and not downloading pdf (only button is appearing on edit view)

but since I'm not using OOB printable and I'm using custom button so may be there will be another solution to fix this issue like we need to add some code for enabling that button to download.