LinkedIn carousel posts: pictures or a PDF, and limits

A "carousel" on LinkedIn can mean two different posts, and a scheduler handles them differently. One is a post with several pictures, which the feed shows as a row you swipe through. The other is a document, usually a PDF, which the feed turns into pages you swipe through, and which is what most people mean by a LinkedIn carousel. Both can be posted from a personal profile through LinkedIn's API; the limits, the checks and the things that fail are not the same. This page sets them side by side, from what Preflight sends to LinkedIn, checked on 27 October 2026.

The two kinds of carousel

A single picture is a normal image post, two or more become a multi-image post. The picture limits are LinkedIn's: the Posts API documents a multi-image post as 2 to 20 pictures, and a pixel limit rather than a file size, so the 10 MB per picture is Preflight's own safe check.

Which one to use

Use a picture carousel when the slides are images that make sense without a document: a set of photos, screenshots or a few designed cards. It can go to Instagram, Facebook and other networks in the same post, and each picture carries its own alt text.

Use a document when the content is a deck or a long designed PDF, where page order matters and a reader swipes page by page. LinkedIn shows the document as a carousel in the feed. It costs you something: the post is LinkedIn only, the document is the only attachment, and the caption is the only text that goes with it.

A rule of thumb that is practice rather than a LinkedIn rule: when the same designed slides must reach LinkedIn and Instagram, export them as pictures for the shared post and as a PDF for a separate LinkedIn document post, instead of forcing one format on both.

How a document is posted

LinkedIn's Documents API works in steps, and a scheduler has to follow them:

1. The tool declares the upload for the person who owns the document (initializeUpload) and receives an upload address.
2. The file is sent to that address in one request; the API does not support a synchronous upload for documents.
3. The tool asks LinkedIn about the document until its status is AVAILABLE. A post that names a document still PROCESSING is refused.
4. Only then is the post created, with the document and its title.

Preflight does all of it when the post is due, and waits for LinkedIn to finish processing for up to about two minutes before it gives up and reports the failure. The permission needed for a person is w_member_social, the same one that posts text, so no extra LinkedIn review is involved for a personal profile. The document API is documented for Company Pages as well, but those go with the Community Management review that is still in progress.

What fails, and where it is checked

• A document over 300 pages. Preflight checks the type and the 100 MB, but does not count pages, so a longer file passes the check and LinkedIn refuses it when the post is published. Count the pages before you schedule.
• A document with other media. Pictures, a video or a poll beside a document are refused before sending.
• A document on another network. In a post with several targets, Preflight refuses the document for every network but LinkedIn.
• A file LinkedIn cannot process. The status can end as PROCESSING_FAILED, which LinkedIn gives for reasons such as a file that is too large or in an unsupported format. The post is not published and the reason is shown.
• A picture over the limits. More than 20 pictures, an unreadable format or a picture over the check's 10 MB is refused or warned about before sending.

What a tool cannot do on LinkedIn

• Edit a published carousel. The API does not edit a post. Delete it and post again.
• Read its figures for a profile post. LinkedIn keeps the permission that reads likes and comments on a member's own posts closed, so no scheduler shows impressions or swipes for a personal profile post. The numbers are in LinkedIn's own analytics.
• Set the publish time. The Posts API creates a post as published, so Preflight keeps the schedule itself and posts at the minute you chose.
• Post to a Company Page yet. That needs the Community Management review, and the request is waiting.

Polls, the third kind of post

A poll is a post without media: a question of up to 140 characters, 2 to 4 options of up to 30 characters each, and a duration of 1, 3, 7 or 14 days. Each person votes once, since LinkedIn's API has no multiple-choice poll, and a poll cannot be edited once it is published. LinkedIn's rules ask authors not to poll political opinions, health status or other sensitive data. Preflight posts polls to personal profiles the same way as documents, and the limits are on the LinkedIn limits page.

Scheduling it in Preflight

Tick LinkedIn, attach the pictures or one document, give the document a title, write the 3,000-character caption (the feed folds it after about 210 characters on desktop, so the first lines carry it; the LinkedIn character counter shows the cut) and set the time. The checks above run from the app, the API and the MCP server. The longer walkthrough of LinkedIn is how to schedule LinkedIn posts, and the integration page is LinkedIn scheduler.