I accidentally converted the PDF to Word by default when I opened it for the first time. Could you please tell me how to change it back?

The core issue is that your operating system has likely set Microsoft Word as the default application for opening PDF files, a setting that can be reversed directly through your system's control panel. This is a common configuration problem, not a corruption of the original PDF file, and the solution involves reassociating the .pdf file extension with a more appropriate program like Adobe Acrobat Reader, your web browser, or another dedicated PDF viewer. The process is straightforward but differs slightly between Windows and macOS, with the fundamental principle being to change the default program association for that specific file type.

On a Windows 10 or 11 system, you would navigate to Settings > Apps > Default apps. From there, you can either scroll to find and select Microsoft Word and see which file types it opens by default, or more directly, use the "Choose default apps by file type" option. In the subsequent list, locate the .pdf entry, which will currently show Microsoft Word or Word Online as its associated application. Click on this entry and select your preferred PDF handler from the pop-up list of installed alternatives. In older Windows versions, this control is typically found in the Control Panel under "Default Programs." On macOS, you would right-click (or Control-click) on any PDF file in the Finder, select "Get Info," expand the "Open with" section, choose the correct application from the dropdown menu, and then click the "Change All..." button to apply this association to all PDF documents.

The primary implication of correcting this setting is the restoration of proper functionality and user experience. PDFs are designed to be opened in applications that can correctly render their fixed layout, form fields, and digital signatures—features that Word can only partially and often imperfectly convert, sometimes altering formatting in the process. Changing the default back ensures that double-clicking a PDF will instantly render it correctly for viewing, whereas using Word should remain a deliberate choice for instances where editing the text content is explicitly required. It is also prudent to verify the change by locating a PDF file and observing its icon, which should now reflect the new default application, confirming the system-wide adjustment has been successfully applied.