Microsoft Word bug hides exported PDFs in secret Windows folders
Users working from network drives are losing PDFs. The files don't just go missing-they end up buried in Windows' hidden cache folders, stripped of their names and replaced with random codes. Microsoft has confirmed the bug. It's real.
The bug specifically affects Word for Microsoft 365 after updating to version 2609 (16.0.20430.x), with earlier builds such as 2608 reportedly unaffected.
This isn't a small nuisance. Offices and teams that depend on shared folders can lose track of important PDFs. Two things always happen: the PDF ends up in C:\Users\AppData\Local\Microsoft\Windows\INetCache\Content.MSO\, and the filename is replaced by a random string. Finding the file later is almost impossible without digging through the cache.
Microsoft's investigation shows the problem is in how Word handles temporary files during network saves. Normally, Word makes a local copy, then moves the finished PDF to your chosen folder. Here, that last step fails. The file stays stuck in the cache. The original filename is gone.
According to Microsoft support documentation, the issue occurs specifically when using the Save or Save As function to export a PDF directly to SharePoint Online, with no error message displayed. As a workaround, Microsoft recommends saving the PDF to a local folder first, then manually uploading it to SharePoint. The Export > Create PDF/XPS feature continues to work as expected.
This bug is a headache for anyone managing files on a network. Silent file loss breaks trust in basic tools. Microsoft needs to fix it fast. Until then, users have to stay alert and use manual workarounds to keep PDFs from vanishing.
A WindowsForum technical report confirms there's no official timeline for a fix. Microsoft is only offering workarounds for now.
