Later on; shortly; afterwards — commonly used in business phrases like 'I will contact you later.'
資料が揃い次第、追ってご連絡いたします。
We will contact you as soon as the materials are ready.
詳細は追ってお知らせしますので、今はお待ちください。
We will inform you of the details later, so please wait for now.
必要書類は追って郵送します。
The required documents will be sent later by mail.
問題が発生したら追って相談しましょう。
If a problem arises, let's discuss it later.
Occasionally used (dated) as a conjunction meaning P.S. or 'additionally' (sometimes written 追而), mainly in older/formal written contexts.
手紙の末尾に追って（追而）と記して補足の説明を書いた。
I wrote '追って' (追而) at the end of the letter and added supplementary remarks.