Even though it resembles a carousel with its scrolling slides, amongst the different formats you can post on LinkedIn, this is actually known as a document. It’s always in PDF format and contains at least 2 pages.
Source: BookMark
In order to post a carousel on LinkedIn, you should first go to your personal dashboard or the dashboard of the company page you want to post from and select the “Start a post” option. From then on, scroll through the post format options on the lower end of the posting window until you arrive at the document option. The icon for it usually hides behind the plus button as it’s second to last. After you click on it, you’ll be invited to upload your file. Remember, only the PDF format is allowed! Once you upload it, you’ll be invited to look through how it visualizes and also pick a descriptive title to give to it. After you’re satisfied with the way it will appear, click on the “Done” button, and you’ll be taken back to the standard post window where you can add any text you desire to your post and go ahead and launch it on your feed.