I was able to sign an admin (read: user) certificate with my own CA and have pulp accept it.

Relevant snippet from the admin certificate that was given to me by pulp:

Issuer: CN=localhost

Relevant snippet from my self-signed certificate:

Issuer: C=US, ST=New Jersey, L=Mickleton, O=Red Hat, OU=Cloud Enablement, CN=redhat.com

The CA information in /etc/pki/pulp/ca.crt:

Subject: CN=localhost

Using my self-signed certificate, I'm able to make commands against the pulp server:

# Show that the admin certificate is the one I signed:
 -> openssl x509 -text -in ~/.pulp/admin-cert.crt | head -6
Certificate:
    Data:
        Version: 1 (0x0)
        Serial Number: 2 (0x2)
        Signature Algorithm: sha1WithRSAEncryption
        Issuer: C=US, ST=New Jersey, L=Mickleton, O=Red Hat, OU=Cloud Enablement, CN=redhat.com

# Make a command against pulp, which will use that certificate:
 -> sudo pulp-admin repo list
No repositories available to list


In my /etc/http/conf.d/pulp.conf:

# Example ssl cert and key files to get you started.
# This MUST match /etc/pulp/pulp.conf [security] 'cacert'.
SSLCACertificateFile /etc/pki/pulp/ca.crt