Bad PDF quality of older articles

I'm sure this is low-priority, but I wanted to make the suggestion anyway: Many older articles in the anthology are extremely hard to read due to the low quality of the pdfs (presumably created by scanning printed papers...?) Maybe some software could at some point be run on those articles to make them more readable.

An example is [C94-2122](http://aclweb.org/anthology/C94-2122). Here's a screenshot for illustration, taken from the 4th page.

Start with the C94-2122 article and the linked screenshot, then inspect how article PDFs are stored or produced in the ACL Anthology. Determine whether the goal is to repair this example, a defined set of older articles, or the whole collection, and establish what PDF quality would count as done.

由索引模型根据 Issue 内容生成。