locale.strings

Overrides for this viewer, whatever the language. strings wins over translations. Some tools have a short label for the toolbar and a full one for tooltips: tool.editText.short, tool.addText.short and tool.managePages.short. Translate both.

new PDFViewer(container, doc, {
  locale: { strings: { 'common.download': 'Save a copy', 'tool.sign': 'Sign here' } },
});