This is a regular verb. It follows the conjugation pattern of the verb falar.
This verb is very common in Brazilian Portuguese. In European Portuguese, libertar or autorizar are often preferred depending on the context.
Present:
A Ana libera o documento.
Ana releases the document.
Preterite:
O Miguel liberou os fundos.
Miguel released the funds.
Conditional:
Eu liberaria o arquivo.
Liberaria o ficheiro.
I would release the file.