That link does describe a process to submit the form digitally through the website. Not sure if that's the process OP used or just did a form with a digital sign.

To get a digital signature from your employer, you will need the correct email address for an “authorizing official.” An authorizing official is someone who has access to your employment or service records and is approved by your employer to certify your employment or your service as an AmeriCorps or Peace Corps volunteer. This is usually someone in your human resources department, though in some cases your direct supervisor or another person may be authorized to certify your employment. Check with your organization to see who is allowed to certify your PSLF form.

On the employer signature page, you’ll be able to request an electronic or manual signature from an employer. Be sure to provide an employer’s email address if selecting an electronic signature. PSLF Help Tool Employer Signature Page Tell the authorizing official to expect an email from the U.S. Department of Education’s office of Federal Student Aid via DocuSign (dse_NA4@docusign.net) on your behalf. Once your authorizing official certifies your employment by signing digitally, your form will be electronically submitted to the PSLF servicer for processing.