If all PDF documents open with edge it means this program is set a default for any PDF files. If you go to Control panel default programs you can choose the default program for PDF files.
If you just want to enter text into a box most free PDF readers including Adobe reader and Foxit will allow you to do this and save the files. If you want to alter edit the PDF file you will need a PDF converter. IcareAll PDF converter and Onekey PDF converter do a reasonable job as I tried both when they were free on the Givawayoftheday . com web site not sure what price they are.
Not all PDF files can be converted, altered or have text inserted especially if the document has been scanned and saved as a PDF file.