Installing multiple versions

Yes.

According to the Installation Guide:

Coexistence and Upgrade
PTC Mathcad Prime 7.0.0.0 can be installed side-by-side with any previous
versions of PTC Mathcad Prime.
The following limitations apply:
• PTC Mathcad Prime 3.0 and PTC Mathcad Prime 3.1 cannot coexist.
• PTC Mathcad Prime 4.0 and PTC Mathcad Prime 4.0 M010 cannot coexist.
• You must install the products in an ascending order (PTC Mathcad Prime 1.0,
PTC Mathcad Prime 2.0, PTC Mathcad Prime 3.0 or PTC Mathcad Prime 3.1,
PTC Mathcad Prime 4.0, PTC Mathcad Prime 4.0 M010, PTC Mathcad Prime
5.0.0.0, PTC Mathcad Prime 6.0.0.0, and then PTC Mathcad Prime 7.0.0.0).
• If you have more than one version of PTC Mathcad Prime installed on your
computer, by default PTC Mathcad Prime files open with the latest version. If
you want files to open in an older version, then you must set file association
manually. Right-click a file, select Open with, and then click the desired
program from the shortcut menu.
• Integration of all previously installed PTC Mathcad Prime versions with
Windchill Workgroup Manager, Windchill ProjectLink, PTC Pro/ENGINEER,
Creo Elements/Pro, and Creo Parametric will no longer work.
• If you previously registered an older version PTC Mathcad Prime with
Windchill Workgroup Manager (using the Application Management utility),
then you must repeat the procedure and register PTC Mathcad Prime 7.0.0.0.
If you have several versions of PTC Mathcad Prime installed on your
computer and you would like to remove some, you must uninstall all of them
in descending order. Then install only the ones you want in ascending order.
• After installing PTC Mathcad Prime 7.0.0.0, you can only use its XMCD,
MCD Converter to convert legacy worksheets into the latest version of PTC
Mathcad Prime.