In request to create preview or create and save preview you need to send body of type multipart/form-data with field file which muste contain a pdf file and pass in header Authorization api key of your project. You can pass query parameters in the url to change width, height or density of preview image. To pass width parameter use w key, for height h and for density d.
In request to get preview you need to pass in header Authorization api key of your project.
Get preview by id and returns it encoded in base64 (Replace {previewId} with id of preview which you want get)