I'd like to use Windows Search for searching through multiple PDFs in one go, but I see that in the Indexing Options' Advanced Options screen, PDF files don't have a registered IFilter:
What is an IFilter, and where can I get the appropriate one?
IFilters allow Windows Search to search within file contents.
Here are three popular PDF IFilters†:
After installing one, you should be able to search within PDF files in the same way that you can for other types of files.
†:This article from 2009 has performance numbers, but they may not apply to current versions of the filters.
An alternative way to search through PDFs is to use the search function of PDF-XChange Viewer. It does not need indexing neither. This is my choice.
You can install the portable version. Hit Ctrl Shift F to get the search dialog:
You can use Mendeley; it's free.
First, add your PDF files and index them. After that, you can search them with auto-complete search.
PDF XChange Viewer, which has a free version available, comes with a built-in iFilter.
Maybe little free tool Pasco from Microsoft Store?
Pasco is a software whose main task is to search for pages in a text (pdf) containing a specified phrase. As the software indexes ebooks, the search result is displayed immediately. Pasco is not only a search engine but also a convenient ebook reader.
Windows 10 has made great optimizations in content search, its goal is to do the search as convenient as Mac. So, if you are using Windows 10, you can build an index between to speed up the search speed, although this process is very slow and long.