Salesforce showFilePreview

gistfile1.js

<!-- This is an example of how to use the function -->
<a id="Title_069Q00000006bam" href="javascript:showPreviewDialog('069Q00000006bam', 'Title_069Q00000006bam', 'PDF');">Cover Sheet</a>

<!-- This is the javascript -->
<script type="text/javascript">

function showPreviewDialogForContentDocument(contentDocumentId, titleElementId) {
    var query = "SELECT Id, ContentDocumentId, FileType, CreatedDate ";
    query += "FROM ContentVersion ";
    query += "WHERE ContentDocumentId = '" + contentId + "' ";
    query += "ORDER BY CreatedDate DESC LIMIT 1";
    var record = sforce.connection.query(query).records;
    showPreviewDialog(record.Id, titleElementId, record.FileType)
}

function showPreviewDialog(contentVersionId, titleElementId, fileFormat) {
    OverlayDialogElement.showFilePreview(
        'docViewerOverlay',
        titleElementId,
        '/_swf/121310/sfc',
        contentVersionId,
        'chatter_bubble',
        'false',
        'docViewerContainer',
        false,
        fileFormat,
        false);
};

</script>