CDR extension is used for several different file types including graphics, disk images or even audio. So there may exist all kind of different conversions. However, the only cdr to pdf conversion that would make sense would be to export Corel graphics (.cdr) as PDF document.
If you have access to CorelDraw then you can simply export your .cdr drawings as .pdf documents. If you do not have access to CorelDraw, you have to use some of the 3rd party utilities that support CDR format to get the job done. A viewer with printing capability would be enough, so you could print your drawing as PDF document instead on paper.
Just keep in mind that Corel formats are proprietary and closed, meaning the latest versions of .cdr files may not always be imported or processed properly in 3rd party software.Open CDR file Open PDF file
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