Redact phrases of text from a PDF using Python and (only) PyPDF2. Would need to modify (trivial) for multiple pages.

redact_pdf.py

import PyPDF2
from PyPDF2 import PdfFileReader, PdfFileWriter
from PyPDF2.generic import StreamObject, DecodedStreamObject
from PyPDF2 import filters

# You change the phrases/text you want redacted and the file paths:
phrases = ["123-45-6789", "YOUR_SECRET_PASSWORD", "YOUR_SECRET_ID"]
read_path = "/path/to/yourpdf.pdf"
write_path = "/path/to/yourpdf-redacted.pdf"


def replace_w_stars(text, phrase):
    return text.replace(phrase, "*" * len(phrase))


def redact(text, phrases=phrases):
    if isinstance(text, bytes):
        text = text.decode()

    for phrase in phrases:
        text = replace_w_stars(text, phrase)

    return text


class EncodedStreamObject(StreamObject):
    def __init__(self):
        self.decodedSelf = None

    def getData(self):
        if self.decodedSelf:
            # cached version of decoded object
            return self.decodedSelf.getData()
        else:
            # create decoded object
            decoded = DecodedStreamObject()

            decoded._data = filters.decodeStreamData(self)
            decoded._data = redact(decoded._data)

            for key, value in list(self.items()):
                if not key in ("/Length", "/Filter", "/DecodeParms"):
                    decoded[key] = value
            self.decodedSelf = decoded
            return decoded._data

# Overload with redaction version
PyPDF2.generic.EncodedStreamObject = EncodedStreamObject

# Read in the PDFs
f = open(read_path, "rb")
r = PdfFileReader(f)

# Force the redaction by merging with itself
page = r.getPage(0)
page.mergePage(r.getPage(0))

# Write out the result
f_out = open(write_path, "wb")
w = PdfFileWriter()
w.addPage(page)
w.write(f_out)
f_out.close()

Thanks for your quick reply riley, what I am saying is that the content of the text variable is encoded or maybe encrypted.

Just a more comprehensive example:

1. I created a .docx file, wrote "This is a very standard text." inside and saved it as PDF
2. If I apply extract_text() method to the page without overwriting class EncodedStreamObject, I correctly get 'This is a very standard text. \n '.
3. If I overwrite the class and place a breakpoint on line 21 above, the text variable has the following content:

/Span <</MCID 0/Lang (en-GB)>> BDC q
0.000008871 0 595.32 841.92 re
W* n
BT
/F1 11.04 Tf
1 0 0 1 56.64 760.68 Tm
/GS7 gs
0 g
/GS8 gs
0 G
[(T)] TJ
ET
Q
q
0.000008871 0 595.32 841.92 re
W* n
BT
/F1 11.04 Tf
1 0 0 1 62.04 760.68 Tm
0 g
0 G
[(h)3(is is a )8(v)-4(er)10(y)-3( )] TJ
ET
Q
q
0.000008871 0 595.32 841.92 re
W* n
BT
/F1 11.04 Tf
1 0 0 1 116.06 760.68 Tm
0 g
0 G
[(s)11(tand)5(ard)5( t)-3(ex)7(t.)] TJ
ET
Q
q
0.000008871 0 595.32 841.92 re
W* n
BT
/F1 11.04 Tf
1 0 0 1 178.46 760.68 Tm
0 g
0 G
[( )] TJ
ET
Q
 EMC  /Span <</MCID 1/Lang (en-GB)>> BDC q
0.000008871 0 595.32 841.92 re
W* n
BT
/F1 11.04 Tf
1 0 0 1 56.64 738.1 Tm
0 g
0 G
[( )] TJ
ET
Q
 EMC