Can I convert a PDF file to a .gif or PNG file?

For GIF use Photoshop.

Yes. Open your PDF

Select "Export" in the right pane or under the Tools tab.

Select Image and the format you want and click Export. Gif is not available.

The gear next to JPEG allows you to set the image quality, and if it's a multipage doc, you can checkmark to export all pages to images.