Fix: Error Opening PDF Attachments in Outlook (Memory Could Not Be Read)

A customer contacted us about an error that appeared every time they opened a PDF attachment in Outlook. The error dialog mentioned a memory read failure, and they had to click OK to dismiss it before the PDF would open (sometimes it would not open at all). The issue only happened when opening PDFs directly from Outlook, not when the file was saved to the desktop first. Reinstalling Adobe Acrobat fixed it immediately.

Symptoms

When you right-click a PDF attachment in Microsoft Outlook and select Open, Adobe Acrobat displays the following error:

Windows – Application Error: The instruction at 0x00007FF8A545BF9D referenced memory at 0x0000000000000018. The memory could not be read. Click on OK to terminate the program

After clicking OK, the PDF may open briefly or fail to open at all. The error only occurs when opening PDFs directly from Outlook. Saving the attachment to your desktop and opening it from there works without any issues.

Cause

Adobe Acrobat’s installation files or cached data have become corrupted. When Outlook hands a PDF attachment to Adobe for direct opening, the corrupted installation triggers a memory access violation. Saving the file to your desktop first bypasses this because it uses a different file access method that does not trigger the same corruption.

Resolution

There are several ways to fix this issue. Start with the quick fix below, and try the alternatives if needed.

Option 1: Reinstall Adobe Acrobat (Recommended)

This is the most reliable fix and replaces all corrupted program files.

1. Open Settings > Apps > Installed apps.
2. Search for Adobe Acrobat.
3. Click the three dots next to it and select Uninstall.
4. Follow the prompts to complete the uninstall.
5. Download the latest version of Adobe Acrobat from adobe.com and install it.
6. Restart Outlook and test opening a PDF attachment directly.

Option 2: Disable Protected Mode in Adobe Acrobat

Protected Mode can sometimes conflict with how Outlook passes files to Adobe. Disabling it may resolve the error without a full reinstall.

1. Open Adobe Acrobat (not from Outlook, just open the application directly).
2. Go to Edit > Preferences.
3. Select Security (Enhanced) from the left panel.
4. Uncheck Enable Protected Mode at startup.
5. Click OK and restart Adobe Acrobat.
6. Go back to Outlook and try opening a PDF attachment directly.

Option 3: Clear the Adobe Acrobat Cache

Corrupted cached data can also cause this error. Clearing the cache forces Adobe to rebuild it from scratch.

1. Close Adobe Acrobat and Outlook completely.
2. Press Win + R to open the Run dialog.
3. Type %APPDATA%AdobeAcrobat and press Enter.
4. You will see a folder named after your Acrobat version (for example, DC).
5. Rename that folder to something like DC_backup.
6. Reopen Outlook and try opening a PDF attachment directly.

Workaround: Save the Attachment First

If you need to access the PDF immediately and cannot troubleshoot right away, use this workaround:

1. Right-click the PDF attachment in Outlook.
2. Select Save As and save the file to your desktop.
3. Open the saved file from your desktop. It will open normally without the error.

Important Notes

• This error is not caused by a corrupted PDF file. The attachment itself is fine.
• The issue is specific to how Adobe Acrobat handles files passed directly from Outlook.
• If the error returns after clearing the cache, a full reinstall (Option 1) is the best long-term fix.
• If your organisation manages Adobe Acrobat through a deployment tool, contact your IT team to push a reinstall rather than doing it manually.

Related Resources

• Outlook Error When Opening PDF Attachments: The Memory Could Not Be Read
• Fix: Action Blocked When Opening Email Attachments in Outlook (ASR)
• Fix: PDF Files Cannot Be Previewed in Outlook or Windows Explorer
• Adobe: Fix installation and update errors
• Adobe: Protected Mode in Acrobat
• Microsoft: Open attachments in Outlook

If you need help with Outlook or PDF issues, get in touch with our team.