I had visited Germany in December 2016 and applied for a multiple entry visa (tourist visa) with a validity of the visa being 30 days (my stay time). I want to visit Germany again.
Would I have to go through all the procedures again and apply again with all my documents?
Your situation is not clear from your description but here's an example of a multiple entry Schengen visa which I will use to explain:
The first row is Country, this will be Schengener Staaten in your visa as well. The second row is validity, you are not allowed be inside the Schengen area before the From or after the To date. This does not mean you can enter on the From date and stay until the To date, there are more restrictions: one, all visitors are under the "out of any 180 day long period you can only spend at most 90 in Schengen" rule and also your visa will have more limitations which I will get to momentarily. The third row is type (it's C in the example and it'll be C in your case too). Then the next is "number of entries" if it's single then you can only enter once. Or it can be MULTiple then you can enter multiple times. Finally, there's the maximum length of any single stay in days. Now you can understand your own visa and reply to your own question based on it.
Edit: if your question is whether you need to file every document for a new visa, yes, absolutely. You will have a hard time finding an official answer to that question but it's easy to find an answer to a very similar, relevant question: What do I have to do if I have lost or misplaced my Indian passport with a valid Schengen visa?
You must apply for a new visa by submitting all documents and payment of visa fees.
So even for reissuing an already granted visa you need to submit all, even more so for an entirely new one.
