Hi,
You will need to use repeater anyway - how else you want to get the data? You need to specify somewhere which document type - what is the source and which field should be used. This is done in the repeater by default and not only in Kentico but it is standard ASP.Net approach.
You can use also the code behind but you will basically replicate the code which is already available in the repeater - re-inventing the wheel. You can check the
API examples to see how to work with documents in the code behind, how to get data of appropriate document.
I do not know what you want to achieve, so from your description I would go for the repeater however, maybe something else is behind and using the API might be more appropriate - this is up to you.
Best regards,
Juraj Ondrus