Update api.md (#1773)

docs/api.md

@@ -1368,13 +1368,13 @@ Page is guaranteed to have a main frame which persists during navigations.
 
 > **NOTE** Generating a pdf is currently only supported in Chromium headless.
 
-`page.pdf()` generates a pdf of the page with `print` css media. To generate a pdf with `screen` media, call [page.emulateMedia({ type: 'screen' })](#pageemulatemediaoptions) before calling `page.pdf()`:
+`page.pdf()` generates a pdf of the page with `print` css media. To generate a pdf with `screen` media, call [page.emulateMedia({ media: 'screen' })](#pageemulatemediaoptions) before calling `page.pdf()`:
 
 > **NOTE** By default, `page.pdf()` generates a pdf with modified colors for printing. Use the [`-webkit-print-color-adjust`](https://developer.mozilla.org/en-US/docs/Web/CSS/-webkit-print-color-adjust) property to force rendering of exact colors.
 
 ```js
 // Generates a PDF with 'screen' media type.
-await page.emulateMedia({type: 'screen'});
+await page.emulateMedia({media: 'screen'});
 await page.pdf({path: 'page.pdf'});
 ```