What is the file size limit when uploading a file into the Files section of NationBuilder?
The file size upload limit is 10mb when uploading files into an individual page under Website>Page>Files. On the other hand, under the page theme you can host a file up to 20mb in size given that it is uploaded to Website>Custom theme>Files. If you'll be uploading more robust files greater than 20mb in size, you may want to consider uploading content on an external host.
Complete and current information on how to use NationBuilder is available in the documentation section.