LinkedIn lets members attach a PDF to a message. That does not establish that a particular outreach tool can attach a PDF in the message type your team uses. A tool may support images but not documents, or support a file in a conversation but not in a scheduled campaign. Check the actual sending path and the recipient's view before building a sequence around an attachment.

01

Start with the message LinkedIn itself can send

LinkedIn's Messaging help lists PDF among supported documents on desktop, iOS, and Android. Its desktop and iOS instructions say to select a file up to 20 MB. That is a limit for the native Messaging flow described on that page, not a promise that every third-party campaign step supports the same files. It also does not make an otherwise unreachable recipient eligible for a message.

Sales Navigator has a different documented path. LinkedIn says its InMail composer can attach PDFs and other listed document formats, with a 50 MB limit per attachment and multiple files in one message. Keep that separate from a regular message to a connection, a connection request note, and a vendor's InMail action. The file limit and recipient access depend on which composer the sender actually uses.

Sources: LinkedIn: attach files to messages, LinkedIn: Sales Navigator message attachments

02

A file feature can shrink when it reaches a campaign

Linked Helper documents an image attachment feature for messages to first-degree connections. Its help page names image formats and a 10 MB tool limit, and says that its image action cannot attach an image to a connection invitation or InMail. That documentation does not establish PDF support in that action. A buyer should not turn the words 'attachment supported' into 'our proposal PDF can go in every step.'

Unipile's own messaging API page says its integration can send attachments including PDFs from a connected user's session. That is a vendor capability claim, not an independent delivery test or evidence of LinkedIn approval. It also describes an API used by an application; a team's chosen outreach product may expose only some of those API capabilities. Ask the actual product vendor to identify the supported file types, message types, plans, and whether attachments work in scheduled steps or only manual replies.

Sources: Linked Helper: image attachment scope, Unipile: messaging API and PDF claim

03

Test the delivered object, not the upload button

Use a colleague who has agreed to receive one test message. Record the sending account, recipient relationship, LinkedIn surface, tool plan, file format, and size. First send a harmless PDF through the native composer that matches your intended message type. Then, if you are evaluating a tool and have accepted its policy implications, send one tool message to the same consenting recipient. Inspect both conversations from the recipient account. Is the PDF an actual downloadable attachment, a preview, or only a URL? Does the document open? Does the tool log agree with what arrived? This is a proposed test, not a result we have observed across vendors.

Repeat the test only for a materially different path you plan to use, such as Sales Navigator InMail rather than a first-degree message. Check a wrong file type and an oversized file before launch without sending them. If the product cannot preview or reject a bad file clearly, require a manual review step. A campaign's 'sent' label cannot prove the recipient received the intended document.

  • Sender and recipient: the exact account, relationship, and message type.
  • File: PDF type, size, filename, preview, and recipient download.
  • Control: rejected uploads, approval point, delivery state, and reply ownership.

Sources: LinkedIn: attach files to messages, LinkedIn: Sales Navigator message attachments

04

Make the policy and content decision separately

LinkedIn says it does not permit third-party software that scrapes, modifies, or automates activity on its website, including unauthorized automated messaging. A vendor's PDF feature does not create an exception, and a successful test send does not settle the account-policy question. The account owner should decide whether to use that sending method before connecting a tool.

A document also asks more of the recipient than a short message. Send it when the recipient requested it or when its contents are clearly relevant; otherwise, a concise explanation and an offer to share the file may be the better first move. If the use case is a small set of known people, LinkedIn's native composer gives the sender a direct way to review the recipient and file. If a vendor workflow is essential, buy only after its exact message type, file behavior, and account implications pass the test above.

Sources: LinkedIn: prohibited software and extensions, LinkedIn: attach files to messages