The combined batch should not exceed 20 megabytes.
For clarity, 1 character = 1 byte.
File sizes will vary depending on document type and contents; for example, 873 pages of plain text is equal to 1 MB. PDFs, Microsoft Word documents, and image files will increase the file size.
Please see http://www.computerhope.com/issues/chspace.htm for more information on disk drive space values.
Please see http://pc.net/helpcenter/answers/how_much_text_in_one_megabyte for examples of how many pages per MB.