I recently received verbal confirmation of an offer of full-time employment from a company I have been doing contract work for. The first email that was sent to me included a .pdf document including: Employment history, basic personal information(email, phone, etc), Social Security Number, Education history to be filled out for a background check. My managers words where "Fill this out, scan it, and send it to me and the HR manager." My question is: "Why would I send this to my personal manager? is that normal procedure?" every job I have been at previously to this on just used the online background checks like ADP or Workday so this is very odd to me. To be honest I don't even know if I am comfortable enough to fill out the information and mail this form to the HR manager that is a few states away. Any thoughts on this would be appreciated because I don't understand the human resources side of this.
It would be perfectly reasonable to try to contact the HR Manager and explain that you aren't comfortable using email for personal information like your social security number - and ask if you could fax or mail (overnight/certified/etc) the form directly to them instead.
If your issue is that you don't want to fill out all the information requested, for whatever reason, you would also want to discuss that with them. If you don't want to fill out something such as full length of history or past education, etc, it's certainly your right to object - but they would generally be allowed (in the US) so consider this as a failure to comply with the background check and thus you would not be hired. So far the information you mentioned being requested is not exceptional and is typical for a background check, and is legally permissible in the US in every jurisdiction I'm aware of.
Note that many companies are moving to background check services, but so far this is not legally required, so companies are typically allowed to conduct their own or retain the information as they see fit (within broader laws of how they must handle that information). So it's not especially unusual they not use an online service.
If it's a legitimate company you've worked for and thus isn't a scam to steal your personal info, I'd suggest you clarify and restrict your concerns and talk with HR directly if there is some specific concern like using email (which is itself reasonable).
Personally, I never provide Personally Identifiable Information (PII) such as SSN, DOB, etc. to a prospective company until I have an offer in hand. There is no reason to provide that sort of information during an interview process prior to being offered the job. Once you are offered and accept the position, you will then be required to provide it for for payroll, citizenship verification, etc.
I used to be an engineering manager and told my new hires to simply bring the required documentation in on their first day where they filled it out and then we snail mailed (or faxed) it to corporate. If it went via fax, I made sure they were standing by to receive it.
Guard your information jealously to avoid identity theft.
With that being said, there is no reason that your manager needs access to data such as your DOB or SSN so I would not send that information to them but only to HR.