I was trying to read the fileds in a pdf form. The Pypdf2 is kicking me with this error. I tired to see if it is encrypted using pypdf2.isencrypted but it is giving me that it is not encrypted. please let me know if any one know this

MCVE

File: https://www.fda.gov/downloads/AboutFDA/ReportsManualsForms/Forms/UCM074728.pdf

from PyPDF2 import PdfFileReader

reader = PdfFileReader("FDA-1572_508_R6_FINAL.pdf")
fields = reader.get_form_text_fields()
print(fields)