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What sort of document we are talking about? PDF? Word? something else? Depending on the document type, there might be ways of exporting them into lower resolution documents that will reduce the file size but have an adverse effect on the quality of the text and images.
Most email servers allow for fairly large files, but if your file exceeds those generous limits, you might want to consider a cloud file sharing service like Box, Dropbox, etc., where you can upload the file and then email a link to your recipient.