Unfortunately, I would say that a post-baccalaureate certificate is not considered graduate work at most schools. Such work is usually considered a graduate certificate. Post-baccalaureate usually means that the certificate was received after a bachelor's degree was already earned by the student. However, this depends on whether grad courses are used for the certificate. Some schools consider high 400-level courses and higher eligible to be applied later to a graduate program.
For example, let's say you majored in Information Technology and earned your bachelor's degree. If you ultimately wanted to combine your love for IT and your interest in Accounting, you could receive a post-baccalaureate certificate in Accounting. If you wanted to receive a second bachelor's degree in Accounting instead, your school could require that you complete an additional 30-36 credits. On the other hand, the certificate could
require as small as 15 credits.
Additionally, a post-baccalaureate certificate could be used by a student who has a bachelor's degree in a program and wants to complete additional study in the same program, wants to receive school teacher certification in an additional subject, or wants to have enough credits to sit for an exam (CPA, etc.).
So, it goes without saying, but a post-baccalaureate certificate is better than not, and will likely result in higher pay. Depending on the number of credits required for the certificate, though, you may want to simply consider a graduate degree. Some post-baccalaureate certificates are 30 credits and some graduate programs are 30 credits, as well. You wouldn't want to earn a post-baccalaureate certificate for the same number of credits that you could have used to earn a master's degree.