Use this SQL to reduce the size of an Umbraco database:

DECLARE @createdDate Datetime = '2014-10-30'

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)


USE [databaseName]
TRUNCATE TABLE [umbracoLog]

Then shrink the database.