Search for a word inside many PDFs
Seventy bills in a folder and the question «which one had that code in it?». Here you pick all the PDFs at once (or the whole folder) and search inside: it tells you which file, which page, and the sentence around it. The files stay on your device.
Why your computer's search finds nothing in PDFs
Because to look inside a PDF the system needs an extra piece that is almost never installed: without it, Windows search only looks at the file name. On a Mac it goes better, but only for PDFs that really do have text in them. And the search inside a single PDF, the one in the reader, has to be opened one file at a time: with seventy files that is an afternoon. Here the files are read once at the start, and from then on searching is instant: you can change the word ten times without re-reading anything.
Scans contain no text, and nobody tells you
This is what wastes the most time: a PDF that comes from a scanner or from a phone camera has no words inside, it has a photograph of the page. Any search finds nothing, and does not say why: it looks as though the document is not there. Here the files with no text are listed by name, and the individual pages with no text inside an otherwise searchable file are counted too, which is the worst case because everything looks fine. To read those pages you need OCR: there is Image to text.
Accents, capitals and the word split at the end of a line
These are the three things that make a search fail when it «should» work. People type resume and the document says «résumé»: here accents and capitals do not count by default, and if you need them exact there is a switch. The third one is invisible: when a word is split by a hyphen at the end of a line, inside the file it is two pieces, and searching for the whole word never finds it. Here the two pieces are sewn back together before searching.
Once you find the line, the PDF opens at that page
Next to every result there is the page number and the sentence around it, with the word highlighted: nearly always that alone tells you which is the right file. If you want to see the document, one tap opens it in your browser's viewer, already at the right page. There too the file goes nowhere: it is opened from your own disk, and the temporary address only lives inside this tab.
What it does not do
It does not OCR scans (it tells you, and sends you to the page that does). It does not search inside Word, Excel or emails, only PDFs. It does not change the files and saves none of them: close the page and it starts over. If you need all the text of a single PDF there is Extract text from PDF, and if you need to see what changed between two versions there is Compare two PDFs.