Recently I had a problem with an Umbraco 4.7.1 installation that had became 10GB in SQL Server and had about 20000 published pages. Since there is no way to do something like this from the umbraco administration panel I had to create a T-SQL to clear the database.
DECLARE @createdDate Datetime = '2012-03-01' DELETE FROM cmsPropertyData WHERE versionId NOT IN (SELECT versionId FROM cmsDocument WHERE updateDate > @createdDate OR published = 1 OR newest = 1) AND contentNodeId IN (SELECT DISTINCT nodeID FROM cmsDocument) DELETE FROM cmsPreviewXml WHERE versionId NOT IN (SELECT versionId FROM cmsDocument WHERE updateDate > @createdDate OR published = 1 OR newest = 1) AND nodeId IN (SELECT DISTINCT nodeID FROM cmsDocument) DELETE FROM cmsContentVersion WHERE versionId NOT IN (SELECT versionId FROM cmsDocument WHERE updateDate > @createdDate OR published = 1 OR newest = 1) AND ContentId IN (SELECT DISTINCT nodeID FROM cmsDocument) DELETE FROM cmsDocument WHERE versionId NOT IN (SELECT versionId FROM cmsDocument WHERE updateDate > @createdDate OR published = 1 OR newest = 1) AND nodeId IN (SELECT DISTINCT nodeID FROM cmsDocument)
Warning if you do not have any TSQL experience be careful because you could easily delete all the data in your database. Always take a backup before making any changes this way.