I have a Custom List that I want to convert to a Document library. All the fields are identical. Is there any easy way of doing this? I'm using SP2013.
There is no inbuilt mechanism say OOTB facility to do such task. But still you can do this with little bit of lazy steps.
Or also you can go with C# custom solution.
For detail information of converting custom list to Document Library you can go with this SharePoint - Convert a list to a library once.
Also if you have document attached in your current list and you want to migrate it into the Document Library then you can go with this Move/Migrate SharePoint List Attachments to Document Library with Created and Modified Date
Let me know whether this approach helpful to you or not.