Post Max Size limits how large a page or file can be on your website. If your page is larger than the limit set in PHP, it will fail to load. Post sizes can become quite large when using the Divi Builder, so it is important to increase this limit. It also affects file size upload/download, which can prevent large layouts from being imported into the builder. You can adjust your max post size within your <a href="%1$s" target="_blank">php.ini file</a>, or by contacting your host for assistance.