It is typically not possible to convert just any kind of TGZ archive (Gzip compressed TAR archive) to a PDF document.
However, if you think that a .pdf document file is inside the your .tgz file, you will need to extract it with some kind of file manager that supports TGZ format, for example 7-zip.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.