Updated FAQ so that it reflect PR 835 (Azure-Samples#868)

* Updated FAQ so that it reflect PR 835

* Update README.md

* Update README.md

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Co-authored-by: Pamela Fox <pamela.fox@gmail.com>

README.md

@@ -355,7 +355,8 @@ Chunking allows us to limit the amount of information we send to OpenAI due to t
 <details><a id="ingestion-more-pdfs"></a>
 <summary>How can we upload additional PDFs without redeploying everything?</summary>
 
-To upload more PDFs, put them in the data/ folder and run `./scripts/prepdocs.sh` or `./scripts/prepdocs.ps1`. To avoid reuploading existing docs, move them out of the data folder. You could also implement checks to see whats been uploaded before; our code doesn't yet have such checks.
+To upload more PDFs, put them in the data/ folder and run `./scripts/prepdocs.sh` or `./scripts/prepdocs.ps1`. 
+A [recent change](https://github.com/Azure-Samples/azure-search-openai-demo/pull/835) added checks to see what's been uploaded before. The prepdocs script now writes an .md5 file with an MD5 hash of each file that gets uploaded. Whenever the prepdocs script is re-run, that hash is checked against the current hash and the file is skipped if it hasn't changed.
 </details>
 
 <details><a id="compare-samples"></a>