static func convertToPDF(from:String, to:String, completion: @escaping () -> Void){
        let pdfDoc: PTPDFDoc = PTPDFDoc()
        
        let options = PTOfficeToPDFOptions()
        options!.setApplyPageBreaks(toSheet: true)
        
        PTConvert.office(toPDF: pdfDoc, in_filename: from, options: options)
        
        let s: PTStamper = PTStamper(size_type: e_ptrelative_scale, a: 0.9, b: 0.9)
        let img = PTImage.create(pdfDoc.getSDFDoc(), filename: Bundle.main.path(forResource: "MainLogo", ofType: "png"))
        s.setPosition(0, vertical_distance: 0, use_percentage: false)
        s.setOpacity(0.1)
        s.setRotation(-50)
        let ps = PTPageSet(range_start: 1, range_end: 20, filter: e_ptall)
        s.stampImage(pdfDoc, src_img: img, dest_pages: ps)
        
        pdfDoc.save(toFile: to, flags: e_ptremove_unused.rawValue)
        
        completion()
    }