Use the button to fill the field.

If your document consists of more than one file, you must encapsulate it in a ZIP arquive. In this case, the  'File Name'  field must be filled with the ZIP arquive name.

The file size must be less than 10000 KiB.

The file content type must be one of those below:
application/force-download
application/msword
application/octet-stream
application/pdf
application/postscript
application/rar
application/vnd.oasis.opendocument.text
application/vnd.openxmlformats-officedocument.wordprocessingml.document
application/x-rar
application/x-rar-compressed
application/x-tex
application/x-zip
application/x-zip-compressed
application/zip
text/html
text/xml
text/plain
text/richtext
image/bmp
image/jpeg
image/pjpeg
image/png
image/tiff