How to merge two PDF files?

I'm trying to merge two PDF's.

Here are the required Python and Django libraries for the project, extracted with pipdeptree preserving the top level of the tree and all libraries are up to date for the maximum available versions.

requirements.txt:

aiocontextvars==0.2.2
aiohttp==3.8.4
aiosignal==1.3.1
amqp==5.1.1
appnope==0.1.3
argparse==1.4.0
arrow==1.2.3
asgiref==3.6.0
asttokens==2.2.1
async-generator==1.10
async-timeout==4.0.2
attrs==23.1.0
autobahn==23.1.2
Automat==22.10.0
autopep8==2.0.2
backcall==0.2.0
bcrypt==4.0.1
beautifulsoup4==4.12.2
billiard==3.6.4.0 # max version
boto3==1.26.134
boto3-stubs==1.26.134
botocore==1.29.135
botocore-stubs==1.29.130
Brotli==1.0.9
cachetools==5.3.0
cairocffi==1.5.1
CairoSVG==2.7.0
case-conversion==2.1.0
celery==5.2.7
celery-stubs==0.1.3
certifi==2023.5.7
cffi==1.15.1
channels==4.0.0
channels-redis==4.1.0
charset-normalizer==3.1.0
click==8.1.3
click-didyoumean==0.3.0
click-plugins==1.1.1
click-repl==0.2.0
constantly==15.1.0
coverage==7.2.5
cryptography==40.0.2
cssselect2==0.7.0
daphne==4.0.0
debugpy==1.6.7
decorator==5.1.1
defusedxml==0.7.1
Deprecated==1.2.13
diff-match-patch==20230430
distlib==0.3.6
Django==4.1.9
django-admin-rangefilter==0.10.0
django-appconf==1.0.5
django-autoslug==1.9.9
django-cachalot==2.5.3
django-ckeditor==6.5.1
django-compressor==4.3.1
django-cors-headers==4.0.0
django-countries==7.5.1
django-debug-toolbar==4.1.0
django-email-extras==0.3.4
django-extensions==3.2.1
django-file-form==3.5.1
django-fixture-magic==0.1.5
django-formtools==2.4.1
django-grappelli==3.0.6
django-guardian==2.4.0
django-import-export==3.2.0
django-ipware==1.1.6 # update
django-js-asset==2.0.0
django-libsass==0.9
django-log-formatter-json==0.2.0
django-loginas==0.3.11
django-model-utils==4.3.1
django-modeltranslation==0.18.9
django-nested-inline==0.4.6
django-oauth-toolkit==2.2.0
django-otp==1.2.0
django-positions==0.6.0
django-recaptcha==3.0.0
django-redis==5.2.0
django-saml-sp==0.7.0
django-sesame==3.1
django-silk==5.0.3
django-social-share==2.3.0
django-sslserver==0.22
django-storages==1.13.2
django-stubs==4.2.0
django-stubs-ext==4.2.0
django-taggit==4.0.0
django-taggit-autosuggest==0.4.1
django-timezone-field==5.0
django-tinymce==3.6.1
django-tz-detect==0.4.0
django-webpack-loader==1.8.1
djangorestframework==3.14.0
djangorestframework-stubs==3.14.0
dnspython==2.3.0
#drf-api-tracking==1.8.2
easy-thumbnails==2.8.5
ecdsa==0.18.0
et-xmlfile==1.1.0
exceptiongroup==1.1.1
executing==1.2.0
extras==1.0.0
fabric==3.0.1
factory-boy==3.2.1
Faker==18.8.0
feedparser==6.0.10
filelock==3.12.0
fixtures==4.0.1
fonttools==4.39.4
frozenlist==1.3.3
funcy==2.0
furl==2.1.3
future==0.18.3
geographiclib==2.0
geoip2==4.7.0
geopy==2.3.0
google-api-core==2.11.0
google-auth==2.18.0
google-cloud-core==2.3.2
google-cloud-translate==3.11.1
googleapis-common-protos==1.59.0
gprof2dot==2022.7.29
greenlet==2.0.2
grpcio==1.54.2
grpcio-status==1.54.2
h11==0.14.0
html5lib==1.1
hyperlink==21.0.0
ics==0.7.2
idna==3.4
incremental==22.10.0
iniconfig==2.0.0
invoke==2.1.2
ipdb==0.13.13
ipython==8.13.2
ipython-genutils==0.2.0
isodate==0.6.1
jdcal==1.4.1
jedi==0.18.2
jmespath==1.0.1
josepy==1.13.0
Js2Py==0.74
jwcrypto==1.4.2
kombu==5.2.4
libcst==0.4.9
libsass==0.22.0
linecache2==1.0.0
lxml==4.9.2
mailchimp3==3.0.18
MarkupPy==1.14
matplotlib-inline==0.1.6
maxminddb==2.3.0
MonkeyType==23.3.0
more-itertools==9.1.0
mozilla-django-oidc==3.0.0
msgpack==1.0.5
msgpack-python==0.5.6
multidict==6.0.4
mypy==1.3.0
mypy-extensions==1.0.0
neovim==0.3.1
numpy==1.24.3
oauthlib==3.2.2
odfpy==1.4.1
openpyxl==3.1.2
orderedmultidict==1.0.1
outcome==1.2.0
packaging==23.1
pandas==2.0.1
paramiko==3.1.0
parso==0.8.3
pbr==5.11.1
pdfrw==0.4
pendulum==2.1.2
pexpect==4.8.0
pickleshare==0.7.5
Pillow==9.5.0
pip==23.1.2
pipdeptree==2.7.1
pipenv==2023.4.29
platformdirs==3.5.1
pluggy==1.0.0
profilehooks==1.12.0
prompt-toolkit==3.0.38
proto-plus==1.22.2
protobuf==4.23.0
psycopg2-binary==2.9.6
ptvsd==4.3.2
ptyprocess==0.7.0
pure-eval==0.2.2
py3-validate-email==1.0.5.post1
pyasn1==0.5.0
pyasn1-modules==0.3.0
pycairo==1.23.0
pycodestyle==2.10.0
pycparser==2.21
pycrypto==2.6.1
pydyf==0.6.0
Pygments==2.15.1
pyjsparser==2.7.1
PyJWT==2.7.0
PyNaCl==1.5.0
pynvim==0.4.3
pyOpenSSL==23.1.1
PyPDF2==3.0.1
pypdf==3.8.1
pyphen==0.14.0
pypng==0.20220715.0
PySocks==1.7.1
pytest==7.3.1
pytest-asyncio==0.21.0
pytest-django==4.5.2
python-dateutil==2.8.2
python-decouple==3.8
python-dotenv==1.0.0
python-gnupg==0.5.0
python-magic==0.4.27
python-mimeparse==1.6.0
python3-saml==1.15.0
pytz==2023.3
pytzdata==2020.1
PyVimeo==1.1.0
PyYAML==6.0
qrcode==7.4.2
rcssmin==1.1.1
redis==4.5.5
regex==2023.5.5
requests==2.30.0
requests-oauthlib==1.3.1
rjsmin==1.2.1
roman==4.0
rsa==4.9
s3transfer==0.6.1
selenium==4.9.1
sentry-sdk==1.23.0
service-identity==21.1.0
setuptools==67.7.2
sgmllib3k==1.0.0
simplegeneric==0.8.1
simplejson==3.19.1
six==1.16.0
sniffio==1.3.0
sorl-thumbnail==12.9.0
sortedcontainers==2.4.0
soupsieve==2.4.1
sphinx-me==0.3
sqlparse==0.4.4
stack-data==0.6.2
stripe==5.4.0
tablib==3.4.0
TatSu==5.8.3
tblib==1.7.0
testtools==2.6.0
tinycss2==1.2.1
tinydb==4.7.1
tomli==2.0.1
traceback2==1.4.0
traitlets==5.9.0
trio==0.22.0
trio-websocket==0.10.2
tuspy==1.0.0
Twisted==22.10.0
txaio==23.1.1
types-awscrt==0.16.17
types-pytz==2023.3.0.0
types-PyYAML==6.0.12.9
types-requests==2.30.0.0
types-s3transfer==0.6.1
types-urllib3==1.26.25.13
typing_extensions==4.5.0
typing-inspect==0.8.0
tzdata==2023.3
tzlocal==5.0.1
unicodecsv==0.14.1
Unidecode==1.3.6
unittest-xml-reporting==3.2.0
unittest2==1.1.0
urllib3==1.26.15 # max version
vine==5.0.0
virtualenv==20.23.0
virtualenv-clone==0.5.7
vishap==0.1.5
watchtower==3.0.1
wcwidth==0.2.6
weasyprint==59.0
webencodings==0.5.1
wheel==0.40.0
wrapt==1.15.0
wsproto==1.2.0
xlrd==2.0.1
xlwt==1.3.0
xmlsec==1.3.13
yarl==1.9.2
zope.interface==6.0
zopfli==0.2.2

And got this error.

File "/code/aca_django/certificates/utils.py", line 10, in <module>
  from pypdf import PdfMerger
File "/usr/local/lib/python3.10/site-packages/pypdf/__init__.py", line 10, in <module>
  from ._encryption import PasswordType
File "/usr/local/lib/python3.10/site-packages/pypdf/_encryption.py", line 68, in <module>
  from Crypto.Cipher import AES, ARC4  # type: ignore[import]
File "/usr/local/lib/python3.10/site-packages/Crypto/Cipher/ARC4.py", line 119, in <module>
  key_size = xrange(1,256+1)
NameError: name 'xrange' is not defined. Did you mean: 'range'?

I have tried with those imports.

from PyPDF2 import PdfMerger
  orr
from PyPDF2 import PdfFileMerger
  or 
from pypdf import PdfMerger

But got the same error.
Any idea ? Thanks.

as said in the comment the error does not come directly from pypdf but rather from its dependency. Specifically pycrypto==2.6.1 which is 10 years old, hence no Python 3 support. Not sure where this dependency came from, but there's (almost) drop-in replacement called PyCryptodome, so you should uninstall pycrypto and install this one instead to see if that will help:

pip uninstall pycrypto
pip install pycryptodome

for more info see PyCryptodome docs