Hi @Noster ,
Since the .pdf format is not a Microsoft Office file extension, “Edit Document” option is not supported directly.
As a workaround, we could download Adobe Acrobat Reader DC and edit pdf file in it, then save file to SharePoint library as following:
Download pdf file and open it in Adobe Acrobat Reader DC >Edit file>Click File>Save As>Add Account>SharePoint Site>Enter Account Name and site URL>Select library to save.
Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.
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