Hi Nidhi,
My site's Moodle version is 2.2. We use the certificate report block. I just installed it on my local 2.9.2 Moodle. I think the block is what you want. However, the 2.8 version block installed in 2.9 BUT does not look good in 2.9.
The good news is that when the student clicks on a pdf icon for a specific certificate, it opens in another window and can be downloaded.
The block shows a list of issued certificates (with PDF links) and has a link at the bottom to a report called "All My Certificates" (which also has PDF links). The visual issue is that the list of issued certificates goes beyond the block boarder on the right. The "All My Certificates" link went to a report that was just what I wanted.
My solution was to copy the url for the report and paste it into an HTML block. The student clicks on the words inside the HTML block and goes to the report. I just tested it for one student that had a certificate in two courses. As with any plugin, that might be enough testing for a production site.
I attached a picture of the dashboard for a student showing the HTML block and another of the report titled "All Previously Issued Certificates".
Not sure this is a solution for you. Just an idea.
Chris