CorelDraw graphics editor has certain issues when a PDF file, that has not been exported in CorelDraw previously, is imported to it. Even slight oddities in the .pdf file can cause CorelDraw to not recognize any data at all. This is typically the case for older PDF documents which, when imported, cause "File is corrupted" error window.
A know workaround for successful import to CorelDraw that might work for certain .pdf files, is to re-save your .pdf again (PDF/A or PDF/X) using latest Adobe Acrobat Reader and try import that PDF document to CorelDraw. It might be possible that exporting to Postscript can yield better result, but in any case you will need CorelDraw as without it, it will be pretty much impossible to recreate CDR file from PDF.
It is unlikely that will finds some reliable pdf to cdr converter online, considering CDR format is proprietary and most programs / online converters just deal with some older variant of the format. Always be mindful when uploading your files to web based converters, you never know where you send them.Open PDF file Open CDR file
A set of applications used by professional graphic designers