I do use 'pdftotext' to do more fine-grained searching if I need to - but for the most part I find that a simple "ls -l | grep <search>" suffices, since this method preserves page title text too ..
I did the same thing for this thread and had no issues with this command, whatsoever:
$ pdftotext WorldBrain\'s\ Memex:\ Bookmarking\ for\ the\ power\ users\ of\ the\ web\ \|\ Hacker\ News.pdf - | grep -i "Print-to-pdf"
Results:".. nothing beats print-to-PDF. Its just awesome." "fancier laid out pages), I Print-to-PDF again after enabling Reader"
pdftotext gets the actual text from the PDF. I don't do this, but I'm sure that you could automate the process of generating a text file for each PDF in a directory with pdftotext and then ripgrep the text files when it's time to search the contents. That would be doable with a makefile or a couple of shell scripts.
E.g:
[$]mdfind -onlyin ~/MyDirectory someSearchTerm
I printed to PDF this HN thread in Chrome (I assume that the PDF printing was done on the system level by OSX -- EDIT yes, from the file: "/Producer (macOS Version 10.15.2 \(Build 19C57\) Quartz PDFContext)"), and none of the page's strings appear as ascii or utf-8 in the document. grep is unable to find any string in that file.
Do you have a specific print to PDF setup? Or a PDF-aware grep..?
EDIT: Seeing the command-line you're using, the search you do is over the files' names, correct? The PDF/(original web page) text content is not indexed, right? Just to make sure I understand correctly.