See this paper for an Uncertainty Analysis for Pressure Modules (PMM) used in 6270A and 2271A Modular Pressure Controllers. A number of these modules can also be used in the 8270A and 8370A Modular Pressure Controllers.
Here's the link to the paper on the Fluke Calibration web site,
Covers these models:
PM500 - added May 2018
PM630 - not yet included but same principles apply, pending update
See this document for 6270A Product Specifications
See this article for an example of calculating the uncertainty in absolute mode of an absolute PM600 module with the 1-year zero drift included, PM600 Absolute Mode Uncertainty - Understanding the RSS Formula
See this article if you're interesting in tracking the calibration coefficients of your module(s) over time, Q-RPT, AutoZero tracking sheet for absolute model Q-RPTs