This sample shows how set and change font name when you generate PDF file with BytescoutPDF.js (Bytescout PDF Generator for JavaScript). 
BytescoutPDF.js provides support for built-in PDF fonts.

// 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");

    // set page size
    pdf.pageSetSize(BytescoutPDF.A4);

    // set page orientation (BytescoutPDF.PORTRAIT = portrait, BytescoutPDF.LANDSCAPE = landscape)
    pdf.pageSetOrientation(BytescoutPDF.PORTRAIT);

    // add new page
    pdf.pageAdd();

    // set font color in RGB format to 0,0,0 - black color
    pdf.fontSetColor(0, 0, 0);

    // set font size
    pdf.fontSetSize(14);

    // BytescoutPDF.js provides support for built-in PDF fonts
    // which are demonstrated in this sample

    // trying Times-Roman
    pdf.fontSetName('Times-Roman');
    // draw text
    pdf.textAdd(20, 20, 'Hello Times Roman!');

    // trying Helvetica
    pdf.fontSetName('Helvetica');
    // draw text
    pdf.textAdd(20, 60, 'Hello Helvetica!');

    // trying Courier-Bold
    pdf.fontSetName('Courier');
    // draw text
    pdf.textAdd(20, 100, 'Hello Courier!');
    

    // return BytescoutPDF object instance
    return pdf;
}

Generated PDF file with custom font (click to view full size):

Click to view full size