The watermark is the free web tool's advertisement, so the answer is tools that do not need to advertise and there are genuinely free clean ones plus one you may already own:

The one you may already own, Microsoft Word itself: recent Word opens PDFs directly, File, Open, choose the PDF and Word converts it to an editable document on the spot, no watermark, no page limit, since it is your own Word doing it. The conversion is a genuine reflow, editable text and Word warns it may not perfectly preserve complex layout, which is honest, but for a text heavy PDF this is the cleanest free route because you already have it.

Google Docs, free and clean: upload the PDF to Google Drive, open it with Google Docs and it converts to editable text, downloadable as Word format, File, Download, Microsoft Word. No watermark, and handles many PDFs well, with the same complex layout caveat as any converter.

The honest scope of all conversion: a PDF made from a text document converts to Word cleanly, while a scanned PDF, an image of text, needs OCR to become editable, which Word and Google Docs both attempt but with varying results and a heavily designed PDF, multi column with graphics, converts to an approximation needing cleanup regardless of tool. Matching expectations to the source type prevents blaming the tool for the PDF's nature.

Why avoid the watermark web tools beyond the watermark: they upload your document to someone else's server, a real consideration for anything sensitive, so the local Word route or your own Google account keeps the document in your control as a bonus over the cleaner output. Adobe's own Acrobat exports to Word without watermark on a paid plan, the reliable paid option when the free routes fall short on complex documents.