Hi @Monika Hall ,
This problem occurs when a PDF iFilter stalls the Windows Desktop search indexer.
To resolve this problem, update any applications that offer PDF file functionality with the latest patches. Then, follow these steps to rebuild the index.
- In Control Panel, select Indexing Options.
- If Indexing Options does not appear in Control Panel, type Indexing Options in the Search Control Panel text box, and then select the Indexing Options search result.
- In the Indexing Options dialog box, select Advanced.
- Select Rebuild.
- Select OK in the Rebuild Index dialog box.
A similar thread for your reference: https://learn.microsoft.com/en-us/answers/questions/1003408/outlook-search-not-working-on-pdf-documents
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