Once a supported file is uploaded to Adobe Send you can create an anonymous link (with basic usage information) or you can send personalized invitations (which provide detailed tracking).
However, Adobe Send does not provide password protection.
What you can do is to use Acrobat (Pro for sure - maybe Standard) to apply security to PDF files such that the password is required to open the file.
Of course you will have to provide the password to those you want to be able to actually open the file.
The "Adobe Send" user community resource is available at:
An FAQ document is available at: