When using the Combine PDFs Automator action along with the Save File As action, the resulting file has the wrong permissions --- the file is unreadable by anyone other than the owner. For unix folks: the permissions are set to 600 or
Automator originally creates the file in some directory which sets the permissions to 600. When the file is saved to its final destination, the permissions are not correct.
In the end of the automator action, put in a unix command to change the permissions to allow others read access. The last step of the automator action should be running a shell script whose contents are
chmod a+r "$@". This seems to work just fine --- it is a hack, however, because it also does not use the permissions that the folder sets by default.
For those interested in the complete automator workflow, you can grab it from here. Note that for it to run, you must have the Save File As action installed. If you just want to see how I have the workflow set up, here is a picture of it.