SearchMyFiles is a freeware tool that allows you search files on your system.
There is an option search files that contain the desired text/string, using the search handlers of Windows operating system. With this feature you can search text inside Microsoft Office documents, .pdf files, and other file Types. If from some reason the PDF search handler doesn't work properly on your system, you can fix this issue by installing the PDF iFilter of Adobe.

In order to search text in .pdf files, follow the instructions below:

1. Download SearchMyFiles and run SearchMyFiles.exe
2. In the 'Base Folder' field, type the drive or folder you want to search the .pdf files.
3. In the 'Files Wildcard' field, type *.pdf
4. In the 'File Contains' line, choose 'Text' from the combo-box and then type the text you want to search in .pdf files.
5. Select the check-box of this option: 'Use Windows search handlers to find text inside Microsoft Office documents and other file types'.
6. Click the 'Start Search' button to start searching the .pdf contain the text you selected.

   

7. After the search process is finished, you should get the list of .pdf files that contain the text you typed.