Tag texts using predefined keywords based on the importance

I want to tag a list of texts using predefined keywords ex: keyword1, keyword2, keyword3. I can easily achieve this using one to one mapping (If keywords exist in the text tagged as important).

But in this way, I cannot find which texts are more important than others(assuming texts contain more than one keywords are more important). To achieve this one I've decided to train word2vec model and extract vectors then calculate cosine similarity between keywords vector and text vector by assuming texts containing more than one keyword will give higher similarity.

I'm not sure whether this method is correct or wrong. Any advices are highly appreciated.

--Thanks--