would like to put limits on user(s) who are uploading files using Apache web server. How do I restrict the total size of the HTTP request body sent from the client under the Apache 2 Web server using the LimitRequestBody option?
To restricts the total size of the HTTP request body sent from the client use LimitRequestBody Directive. You can add this directive using .htaccess file or httpd.conf file under virtual host or directory configuration options. You can set value (in bytes) from 0 (unlimited) to 2147483647 (2GB) that are allowed in a request body. Without such configuration you may get the error such as, “Request entity too large. Request exceeds the capacity limit“, or “413 Request Entity Too Large” on your Linux or Unix server. Hence, we need to fix this issue.
For example, limit /var/www/vhost/cyberciti.biz/wp-uploads to 100K, you might use the following directive (add to .htaccess or httpd.conf file):
<Directory "/var/www/vhost/cyberciti.biz/wp-uploads"> LimitRequestBody 102400 </Directory>
Reload your web services
A note about PHP config options apart from using LimitRequestBody – Apache limiting user upload file size
Apart from Apache server config with the LimitRequestBody. You need to set post_max_size and upload_max_filesize
Fuente: https://www.cyberciti.biz/faq/apache-limiting-upload-size/