A Woburn man has pleaded guilty and been sent to jail on charges he possessed and disseminated child pornography and obscene matter over the Internet. Raymond Lefebvre, age 40, of Woburn, pleaded guilty late Wednesday to Possession of Visual Matter of a Child in a State of Sexual Conduct with Intent to Disseminate (1 count), Possession of Visual Matter of a Child in a state of Conduct (2 counts), and Possession of Obscene Matter with Intent to Disseminate (one count).