JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I understand that you want to allow users to upload a file upto 300mb. You can achieve this by adjusting the file size property of upload field to 307200.
However, this amount of file size cannot be uploaded on a Free account since it is limited to store 100MB only. But on the premium subscription plan, you can store upto 10GB. You are free to upgrade/downgrade/cancel the subscription anytime and as per your requirement. Please refer to our pricing page for more information on taking advantage of paid plans.
Hope this information helps. Please get back to us if you have any other questions. We will be happy to assist you.