A PDF must reside online before it can be shared on Twitter. This means that you can't upload and attach it to a tweet, like you can with a photo or video. Instead, you provide a link to where the PDF can be found on the Web. By clicking or tapping the link, followers can then access and read the file.
Store PDF Online
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Upload the PDF to your website, blog or cloud storage service, such as Dropbox, OneDrive or iCloud -- then, copy its Web page address or the URL link for pasting into a tweet. You may also use special store-and-tweet Web services -- such as TwitDoc, FileSocial and FileTwt (see links in Resources) -- to share your PDF, provided that you're comfortable authorizing them to use your Twitter account. These services typically impose size and time restrictions on uploaded files.
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Shorten Link and Tweet
URL links can be extraordinarily long and given your 140-character tweet limit, you'll want to shorten them. Conveniently, Twitters' built-in t.co service handles this for you; Simply paste your PDF link into the Tweet box and it is automatically shortened before dispatch. You can't opt out of this service.
Twitter’s URL-Shortening Advantage
Twitter's shortened link will always be 22-characters long, leaving you with a predictable 118 characters for an accompanying message. While third-party URL shortening services -- such as Bit.ly -- can achieve much shorter links, Twitter-generated links can warn users when a tweet's linked content may be malicious. Consequently, Twitter's shortened links are more reassuring and inviting to users.