The file extension CWK indicates a file created with ClarisWorks, later called AppleWorks, an early word processing program and office suite for Mac and Windows. Since ClarisWorks is not a commonly used program anymore, converting a CWK document to PDF will make it easier for others to view the document without having to purchase special software. The conversion may give you trouble, however, if you do not have a program on your computer that can read CWK files. Tips Writer Bio
