[Feature Request] Knowledgebase search result: add PDF page number

## Describe the solution you'd like

For longer PDF documents it would be great to not only get the PDF link itself, but also the page numbers where the results have been retrieved. Is there any way to implement this?

## Why the solution needed

Have a more precise result of where the result is located in a (large) PDF.

The issue does not name any files, tests, or entry points. Start by tracing how knowledgebase search results are assembled and rendered, then determine whether PDF page metadata is available at retrieval time. Done means relevant results include the PDF page number alongside the existing link.

Written by the indexing model from the issue text.