Examine source code of WebToPDF

{
  "manifest_version": 2,
  "name": "WebToPDF",
  "version": "1.1resigned1",
  "description": "Adds a browser action icon to the toolbar. Click the button to download as pdf",
  "icons": {
    "48": "icons/logo.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/logo.png",
    "default_title": "WebToPDF",
    "default_popup": "popup/download.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a9bd1d11-ad0c-444c-923d-f0acd5eb61e5}"
    }
  }
}