The best solution I've found till now is to just create a text file with the same name as the pdf.
Yes:
Acrobat searches the PDF body text, layers, form fields, and digital signatures. You can also include bookmarks and comments in the search.
https://helpx.adobe.com/acrobat/using/searching-pdfs.html
Other PDF applications do it too.
The best solution I've found till now is to just create a text file with the same name as the pdf.