fixing the url.

Author: sambitdash

README.md

@@ -130,6 +130,7 @@ to the PDF document [library](http://www.stillhq.com/pdfdb/db.html) maintained
 by [mikal@stillhq.com](mikal@stillhq.com). Some of the files have to downloaded
 from the database for unit testing of the documents. Some files are also
 included from
-[openpreserve](/openpreserve/format-corpus/tree/master/pdfCabinetOfHorrors).
+[openpreserve]
+(https://github.com/openpreserve/format-corpus/tree/master/pdfCabinetOfHorrors).
 These files can be distributed with
 [CC0](https://creativecommons.org/publicdomain/zero/1.0/).