Last Updated on September 14, 2023 by Dave Farquhar
PDF, or portable document format, is a somewhat problematic but very useful file format, especially for people who conduct a lot of historical research. But the problem with having megabytes or gigabytes of historical data on your computer is finding the information you are looking for. Here’s how to make PDFs searchable in Windows, because by default they are not.
Is the PDF itself even searchable?
Not every PDF actually contains text. If the document was scanned, it is possible that every page is simply an image, with no computer readable text in it. For the PDF to be searchable in Windows, it needs to contain computer readable text.
To check this, open the document in whatever tool you normally use to view PDFs. Then try to highlight some text like you would if you were going to copy some text out of the document to paste it into another document. If you can highlight text, the PDF has computer readable text in it. If you cannot, then the document needs OCR before it will be searchable.
For that, you need software.
If you have the full-blown Adobe Acrobat, it has the ability to perform optical character recognition on a document, adding a computer readable text layer. There are a number of other commercial products that can perform the same function, such as ABBY Finereader. These tools are great if you want a user friendly interface and have a small enough number of documents that you won’t mind running through them one at a time.
If you have a large number of documents, and no budget, there is a fantastic open source tool called OCRmyPDF. That’s what I use to perform OCR on documents in bulk, and I’m thrilled with it.
Once you confirm your PDFs contain text, there are two more stops to perform.
Adding the PDF Ifilter
Although Windows does come with tools that can view PDFs, it does not come by default with the library it needs to index PDFs. Adobe quietly provides one… Too quietly. It’s not even clear what tools they bundle the Ifilter with.
You can download the Adobe’s Ifilter component and install it. Adobe doesn’t make it especially easy, and not every web browser will like the link I am providing. Chrome refuses to download executable files over plain http connections, for example. But I can confirm that Firefox will visit this URL and let you download the file, albeit with some protest.
If you prefer, use the Chocolatey package manager to install it. If you have Chocolatey installed, you can simply run the command choco install pdf-ifilter-64 to install it and then running choco upgrade all every month or so will make it easy to keep up to date.
Once you manage to download it, there isn’t much to the installation. Double click on the file to run it. Accept the license agreement, accept the defaults, and click Next a lot.
Enable PDF indexing
Now that you have the Ifilter binary installed, you need to make sure Windows is actually indexing those files. First, make sure the directory where you store your PDFs is being indexed. If you store your files in your main documents directory, you’re good. If you store them somewhere else, such as on a second hard drive, you will need to make sure that drive or whatever location you store your documents in is indexed. Go to Windows Search Settings. (Just click the Windows button in the corner, then type search settings to pull it up). Normally, Windows limits what directories it indexes. Add the place your PDFs are stored to the list of places it indexes, if you don’t want to have it index your whole machine.
Finally, you need to make sure PDFs themselves are being indexed. Go back to Windows search settings, scroll down to the end, to Advanced Search Indexer settings. Click Advanced, then click File Types. Scroll down to PDF and make sure the box is checked and you choose the option Index Properties and File Contents.
After you enable indexing, it can take some time for Windows to fully index all of your PDFs. But once they do, you’ll be able to search the contents of PDFs from Windows Explorer.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.