Go to File menu > choose Optimize Catalog to optimize it.
Refer this article to optimize the performance of Lightroom : How to improve and speed up Photoshop Lightroom performance
Deleting edit history will reduce the catalog file size. Just make sure the company's LR users are OK with removing it. I use it rarely and only during the initial editing phase. How large is the catalog file(s)?
Going on 6 GB. this computer was last optimized in March 2014
How many image files in the catalog? I would backup the current catalog using the below settings, which will also perform an optimization. THat way if something goes wrong during the optimization you have a current catalog backup. With a 6GB catalog file it will take many minutes to complete.
(EDIT: Changed screenshot)