I downloaded the most current trial version of PrintLife from their website and I get the same 'Invalid Code Signature' error on this version as well. However, I downloaded the trail version of another Chronos app and that installed and worked fine.
Chronos does seem to be a legit company, I've used a number of their apps, and like them, but they have essentially zero tech support for any of their apps. I've searched for a telephone number but to no avail.
I also d/l'ed the latest version of PrintLife from Chronos's website with the same results you got, but I'd be inclined to give them some time, and I'd check their website, not MacUpdate, because v 4.0.1 was posted to the App Store on May 5, 2017, whereas it wasn't posted to MU until June 21, 2017.
I note that Chronos's tech support policy is "
Chronos aims to offer its customers a first-class support experience. Please visit our Support web site to get answers to any questions or problems you may have or to contact one of our support technicians."
(Where did you find a street address to which to send snail mail?)
