Does the Size of Azure Search Index impact performance/accuracy?

I have 1000 pdfs(200 pages each).
I need to add each pdf to the index (as small text chunks and relevant metadata, for example 200 chunks per pdf) in Azure Search Index
Have already hit the limit of 50 max possible Search Indexes after which I am getting prompted to delete few indexes..

I am now planning to just have 1 Single Search Index and add all 1000 in a Single Search Index. I then plan to use filtering in the .search method and will filter based on the pdf name.

Does this plan have a downside ?

Using a single large index for all documents related to a given application is the right approach for this. As you mentioned, you can use a filterable field with the name of the document to scope searches. This also has the advantage that if you ever need to search across all or multiple documents, it'll just work.

In terms of downsides:

• At the volumes you're describing (~200K pages), the size of the index won't be a problem at all. If you had 100s of millions or billions of pages, there's a point where partitioning the index would be better, but that's more work and I would avoid it if you don't think you'll hit that kind of data volume.
• If the documents have very different data distribution properties, for example very different vocabulary, then mixing the documents could cause some statistical oddities during scoring (e.g. a term that's rare in one document might be common in the rest of documents, skewing statistics that way).

I'm listing downsides for completeness, from the description of your scenario, most likely a single index will be just fine.