Use DocSend2PDF with Python. I am not affiliated with DocSend2PDF or DocSend in any way.
pip3 install docsend2pdf
from docsend2pdf import DocSendClient
docsend_client = DocSendClient()
docsend_client.download(
file_name=FILE_NAME # Required, (e.g. 'output.pdf')
url=URL, # Required (e.g. 'https://docsend.com/view/abc123')
email=EMAIL, # Optional
passcode=PASSCODE, # Optional
searchable=True, # Optional, defaults to True
)