You can change the Jasper Server language indeed, by changing the locale at the login page by expanding the option "Show locale & time zone", then selecting the desired language:
In the example, the "pt_BR - português (Brasil)" was selected, and then words are appearing localized (Portuguese):
However, reports content still appears in English (title and content):
Jasper Reports Server 6.3.0 / 6.4.2
CA Service Desk Manager 14.1 / 17.x
The jasper reports that we ship out of the box, report names & report titles were not localized. They were built for English language only. This would be the case for 17.1, 17.0 and older release where CABI Jaspersoft based reports are shipped.
In the upcoming releases, where we are building domains for operational reporting, out of the box content would also be localized.
With respect to documentation, if respective language bundles are checked in, then based on the language selection, localized names would be displayed. But the out of the box report names & report titles would not.
In case you need the SDM reports localized, you would need to edit them using Jasper Studio tool.
Supported Languages - CA Business Intelligence JasperReports® Server - 6.4.2 - CA Technologies Documentation
How to configure Jasper Studio for editing existing reports and creating new reports for CA Service Desk Manager data on Jasper Server
Jaspersoft Community - Documentation - TIBCO JasperReports Server Administration Guide - Localization