You should be aware that even for asymmetric encryption, only a one-time document-specific key will be encrypted with the asymmetric algorithm. The document itself will always be encrypted using a symmetric cipher.
This is how the same document can be encrypted for multiple recipients efficiently, without duplication all the data. First the document is encrypted with a symmetric key, which is then encrypted with the public key of each recipient. This information will be prepended to the actual encrypted document.
But for bulk data encrypting good symmetric (AES, CAST5, etc.) is both more secure and significantly faster.