2018 年购于数码荔枝，可以绑定到自己邮箱，在 expert3 上激活 expert2 所拥有的功能。
官方介绍：
Existing customers, you keep all the features you had before
If you already purchased PDF Expert for Mac:
All the features you had in PDF Expert for Mac are still here, without a subscription. Forever. If you’d like to use new features like OCR and PDF to Word conversion, you can upgrade to Premium with 50% off the first year. This also unlocks the iOS version and gives you access to all the powerful new tools we plan to bring in the future. If you are subscribed to PDF Expert on iOS, you can upgrade and use the app across iPhone, iPad, and Mac at a discounted price of $64.99 for the first year (then $79.99/year).
联系： https://t.me/mdt9PAYZl8j2 （二手交易不用找 bot ，先码后款，因为我没在 3 上激活过所以不太确定具体激活后是咋样的）
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