Are there PDF files that pdfgrep cannot search yet display with xpdf?

I am on a Chromebook running Debian with pdfgrep v2.1.2. I have a PDF file of the full Mueller Report that I occasionally want to search for particular references. Pdfgrep of the file for any pattern *quickly* returns nothing. Pdftotext cannot seem to handle it and produces a very short file of junk. Pdfinfo produces the following:

Title:           
Creator:         RICOH MP C6502
Producer:        RICOH MP C6502
CreationDate:    Wed Apr 17 15:23:21 2019 PDT
ModDate:         Wed Apr 17 15:59:41 2019 PDT
Custom Metadata: no
Metadata Stream: yes
Tagged:          no
UserProperties:  no
Suspects:        no
Form:            AcroForm
JavaScript:      no
Pages:           448
Encrypted:       no
Page size:       792 x 612 pts (letter)
Page rot:        270
File size:       145509756 bytes
Optimized:       yes
PDF version:     1.6

Could pdfgrep not be compatible with the PDF version of the file?