I thought I'd post this as an issue I came across today.

I noticed that the contents of PDF files were not showing up in Searches from File Explorer (and I guess Cortana).

I should be able to type in a word from a PDF file and, as long as the PDF file is in an indexed location, this should appear in search results.

It turns out that this is a problem which occurs when Adobe Reader is installed, apparently affecting x64 versions of Windows.

The search "iFilter" for PDFs gets broken, so the search doesn't index them. When looking in Indexing Options | Advanced | File Types, the entry for .pdf says "Registered iFilter is not found".

This seems to be the relevant page on Adobe's Knowledge base:

Note that it says it's fixed in Adobe Reader 11.04, but I'm using a later version of Adobe Reader and still had the problem in Windows 10 x64.

iFilter PDF search doesn't work on Windows 8 x64

Windows 8 64 bit provides native support for the PDF iFilter, which enables indexing PDFs so you can search for specific text. Installing Acrobat or Reader 11.0 breaks this feature. It overwrites the Windows 8 native iFilter registry entry with the product registry entry.


Do one of the following:

  • Update to Acrobat/Reader 11.0.4 or higher. The issue is fixed in version 11.0.4. [DavidY:But it wasn't for me]
  • PDF iFilter 9 is not supported on Windows 8, update to PDF iFilter 11 from here.

If you cannot update your Acrobat/Reader or PDF iFilter, here is the workaround.

Workaround: Restore the registry entry to the Windows 8 native entry as follows:

  1. Go to HKEY_CLASSES_ROOT\.pdf\PersistentHandler. Create the key if it does not exist.
  2. Verify that the value is 1AA9BF05-9A97-48c1-BA28-D9DCE795E93C. If the Acrobat or Reader install overwrote the entry with F6594A6D-D57F-4EFD-B2C3-DCD9779E382E, return it to its original value.
    [DavidY Note: if you do this. make sure the values are in curly brackets, like {1AA9BF05-9A97-48c1-BA28-D9DCE795E93C} ]
  3. If you have any third-party PDF iFilters installed, reinstall them.
  4. Restart the Windows Search service:
    1. Go to Task Manager > Services.
    2. Select WSearch.
    3. Right-click, and then choose Restart.
    4. [DavidY: I believe you also need to going into Indexing Options | Advanced | Rebuild, to regenerate the index for all existing files]