WebViewer 7.1 adds support for an experimental text edit feature in the UI which allows you to edit text directly on PDF files. After selecting text a button appears in the text selection menu which allows you to change the text.

linkEnable text editing feature

This feature requires the WebViewer Full API, which can be enabled by passing the option fullAPI: true into the WebViewer constructor and you also need to enable the text edit button in the UI.

WebViewer({
  fullAPI: true,
  // other options
}, document.getElementById('viewer'))
.then(() => {
  // Enable text edit button
  instance.enableElements(['editTextButton']);
});

You will see the text edit button after selecting text