This comes up a lot. Sometimes you search for a document and you can’t find it but you find a whole lot of other documents you don’t need. So what is searchable and what isn’t?
If you have permissions to a specific document, you will automatically be able to search for this document wherever you are in your SharePoint site.
The search will take your keyword and match it with the file name, the title of the document and any associated tags and metadata. It will also match it with the contents inside of the document.
But here is a caveat. If you have a Word document – then it's pretty easy. If you have a PDF scan of an image – then search won't pick up any of the words inside this scan. Surprisingly, the search will pick up the text from scanned images.
The key to accurate search is to use more than one keyword and combine keywords to eliminate generic results.