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
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.
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.
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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.