This sample demonstrates how to change page orientation when creating PDF file in JavaScript with BytescoutPDF.js (Bytescout PDF Generator for JavaScript).
In the sample, you’ll see page orientation set to both portrait and landscape.

// function that creates BytescoutPDF instance (defined in BytescoutPDF.js script which have to be included into the same page)
// then calls API methods and properties to create PDF document
// and returns created BytescoutPDF object instance
// this CreatePDF() function is called from Sample.html
function CreatePDF() {
    // create BytescoutPDF object instance
    var pdf = new BytescoutPDF();
    // set document properties: Title, subject, keywords, author name and creator name
    pdf.propertiesSet("Sample document title", "Sample subject", "keyword1, keyword 2, keyword3", "Document Author Name", "Document Creator Name");
    // add a page with portrait orientation
    pdf.pageSetOrientation(BytescoutPDF.PORTRAIT); // BytescoutPDF.PORTRAIT = portrait, BytescoutPDF.LANDSCAPE = landscape
    pdf.textAdd(50, 50, 'Portrait page orientation', 0);
    // add a page with landscape orientation
    pdf.textAdd(50, 50, 'Landscape page orientation', 0);
    // return BytescoutPDF object instance
    return pdf;

Generated PDF file with portrait and landscape page orientations (click to view full size):

Click to view full size