I'm working on my thesis and I'd like to see if some documents that I'll use have been used before to see if the topic and focus I'm working on has been done before. At the moment it seems it hasn't, I looked for citations in Google scholar and it has only 1 citation, Academia.edu has around 2000, but I must have Academia Premium to see it. Is there any other way to look for citations? Is it worth to have Academia Premium?
For biology and chemistry-related publications you can use Europe PMC as a search engine - it indexes citation counts and is free to use. Since it only shows open citations (those that publishers have made freely available), the citation counts will be smaller than those for the Web of Science, but you can access that info without subscribing. Alert: I work for Europe PMC.
For papers in mathematics and related fields, arXiv tracks how many times a paper has been cited by other arXiv papers. In some fields this might not be useful, but in mathematics/computer science/some fields of physics it’s going to be a very good approximation.