Hello Ratnesh,
Direct editing of a quote in a PDF within Salesforce is not possible. However, you have the option to edit the template from which the PDF is generated. By altering the template, subsequent PDFs generated from that template will reflect the changes you’ve made.
Aditya has provided an answer on this topic that you can refer.
For more details on generating and customizing quote PDFs in Salesforce, you might find this resource helpful: https://arrify.com/generate-quote-pdf-salesforce/.
I hope that helps! Let me know if you have any further questions.