es,
       combineFilesOperation = CombineFiles.Operation.createNew(),
       input1 = PDFServicesSdk.FileRef.createFromLocalFile('combinePagesInput1.pdf', CombineFiles.SupportedSourceFormat.pdf),
       input2 = PDFServicesSdk.FileRef.createFromLocalFile('combinePagesInput1.pdf', CombineFiles.SupportedSourceFormat.pdf);

 combineFilesOperation.addInput(input1);
 combineFilesOperation.addInput(input2);

 combineFilesOperation.execute(executionContext)
     .then(result => result.saveAsFile('CombinedPDF.pdf'