Fix the "File Is Not Trusted" Error When Opening a PDX Index
Question details
The user needs to resolve a security error that prevents them from opening a PDX index file remotely over a VPN connection.
- Product
- Adobe Acrobat
- Device & OS
- not provided
- Scenario
- Accessing and opening a PDX index file stored on a remote network through a VPN connection.
- Observed behavior
- The PDF viewer blocks the PDX file with a "File is not trusted" warning, even though the same file opens correctly on local computers.
Ensure your VPN connection is active and stable, and verify that the PDX index file and its linked PDFs originate from a safe, recognized source before modifying your security configurations.
Add the Network Path to Trusted Locations
By adding the VPN's network drive path to your PDF software's Privileged Locations, you can bypass the security warning for safe files.
Modern PDF readers apply enhanced security features that restrict files opened from remote or unknown network paths by default. To fix this, you need to explicitly whitelist the specific VPN directory where your PDX and PDF files are stored.
Launch your PDF software and navigate to "Edit" > "Preferences" (Windows) or "Acrobat" > "Preferences" (Mac) in the top menu bar.
Select "Security (Enhanced)" from the Categories list situated on the left-hand panel.
Scroll down to the "Privileged Locations" section and click the "Add Folder Path" or "Add Host" button.
Browse and select the remote network folder accessed via your VPN that contains the PDX index and its linked PDF files, then click "OK".
Click "OK" at the bottom of the Preferences window to save your changes, then try opening the PDX index file again.
Verify VPN Access Permissions to Linked PDF Files
Ensure that your VPN connection grants sufficient read permissions to all the individual PDFs referenced by the PDX index file.
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Frequently Asked Questions
What exactly is a PDX file?
A PDX file is an index file used by PDF software to group and search across multiple PDF documents simultaneously. It acts as a catalog, allowing users to find specific text across a large batch of PDFs much faster than searching each file individually.
Why does the PDX file work locally but show a 'not trusted' error on a VPN?
PDF software applies stricter security protocols, such as Enhanced Security sandboxing, to files accessed over external networks or VPNs to prevent malicious code execution. Local files are generally treated with a higher baseline level of trust by default.
Is it safe to disable Enhanced Security entirely to fix this?
Disabling Enhanced Security globally is not recommended, as it removes critical protections against potentially malicious documents downloaded from the internet. It is always safer to keep the feature enabled and add specific, known-safe network folders to your Privileged Locations instead.
