Hello,
This can be achieved easily using Kentico
CMS. In fact, your approach is correct - you need to have the old URL as an alias for each document in order to have this document accessible under the old URL. There is a functionality which creates aliases automatically for all child documents when changing URL of their parent - the
Remember original URLs when moving documents option needs to be set in
Site Manager -> Settings -> Your_Site -> URLs and SEO.
Furthermore, to achieve permanent (301) redirect, you need to set the following two settings at the same location:
Allow permanent (301) redirection and
Redirect document aliases to main URL.
This way you'll be redirected to new URLs with 301 response in a header. You can check that using e.g. Firebug add-on.
Best regards
Ondrej Vasil