This may be regionally different, but as a hiring manager I don't think I've received a resume or reference on paper since about 1995.
The likelihood is that if it was accepted by an employer, HR would scan to email to the hiring manager and interviewers, so your choice of paper is unlikely to be noticed. I've also had resumes copied and pasted into emails, even from Linkedin profiles (with all formatting lost). Additionally many employers use Application Tracking Systems (ATS) to do first level screening, so your paper resume will not get past that.
Most "references" are, in my experience as a hiring manager and job changer, just employment verification, and in the rare actual reference, they usually like to talk to the referee to ask specific questions and gauge the reaction of the referee (in case of double meanings on paper to avoid saying anything slanderous about a possibly troubling employee).
So don't over think it, concentrate on what the doc says, not the paper.