Or if you prefer to fix it directly via Odoo UI, go to Settings → Technical → Reporting → Reports, find your duplicated "Custom PDF Quote" report, and manually fill in the Attachment field with the same expression as the original (e.g. object.name + '.pdf') and tick the Reload from Attachment checkbox. The attachment field is a Python expression evaluated against the record (object), and attachment_use tells Odoo to store and reuse the generated PDF rather than regenerating it each time both are silently left empty during duplication, which is why the Quote Builder PDF attachment stops working on the copy.

Hope it helps

Hii,

Try this 

Go to Settings → Technical → Reports → Reports

Find your custom report

Enable these fields:

Attachment Use : ✔Checked

Attachment :

(Custom PDF Quote - %(name)s)

Or use the same as original:

(Sale Order - %(name)s)

I hope it is usefull