If I compiling xpdf v3.04 from original package search works fine.
If I compile the debian version of xpdf v3.04 you obtain an executable
linked to libpoppler126
Take a random pdf file for example:
https://www.cs.dartmouth.edu/~sergey/cs258/ABI/UlrichDrepper-How-To-Write-Shared-Libraries.pdf
The word 'hash' appears 62 times in this file:
$ps2ascii UlrichDrepper-How-To-Write-Shared-Libraries.pdf | grep -i hash | wc -l
62
Open the above pdf in xpdf on page 1 and then Find text: 'hash' - nothing is found
go to page 5 and try to find 'hash' again - hash if found several times
in pages 5 to 10 but nothing after