The first thing to do is check how we see your document. You can do this by using our debug page. This will tell you if we can download the document and any issues impacting its indexing. The debug page will also preview what a basic search result including the document will look like.
If we can't download the document, then it's likely a corrupt file. Some systems may still be able to open the file, but not all. We recommend re-saving or exporting with a different program or version.