简单的测试了下ocr效果，如图
Acrobat ocr:
The set of all tangent vectors to an n-dimensional manifold M at a point x
forms an n-dimensional linear space Tx = T"M, the tangent space to M at the
Abbyy 16:
The set of all tangent vectors to an n-dimensional manifold Af at a point x
forms an n-dimensional linear space Tx = TXM, the tangent space to M at the