Examine source code of SaveTabs PDF

{
  "manifest_version": 2,
  "name": "Save Tabs as PDF",
  "version": "1.0",
  "description": "Saves the URLs of all open tabs into a PDF file.",
  "permissions": [
    "tabs",
    "downloads",
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Save Tabs as PDF",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "savetabspdf-unique-79902@addon.com"
    }
  }
}