For the common tasks, compressing, merging, rotating and splitting PDFs, browser-based tools that run on your own device are a free alternative to Adobe Acrobat's online tools. Acrobat's web tools process your file in Adobe's cloud and ask you to sign in with an Adobe account for a number of operations, while client-side tools need no account and never upload the document.
Free online PDF compressor. Re-save a PDF to trim its file size in your browser and see the before and after numbers. Private, nothing uploaded.
Open Compress PDF → Free toolFree online PDF merger. Combine several PDF files into one document, drag the files to reorder them, then download the merged PDF. Nothing uploaded.
Open Merge PDF → Free toolFree online PDF rotator. Turn every page or selected pages of a PDF by 90, 180 or 270 degrees and download the fixed file. Private, nothing uploaded.
Open Rotate PDF →Adobe's online PDF tools are capable and polished, but they are cloud services: the file you add is uploaded and processed on Adobe's side, and several operations prompt you to sign in with an Adobe account, with the more advanced features belonging to the paid Acrobat Pro subscription. For a quick one-off merge or rotation, creating an account and uploading a private document is more friction than the task deserves.
Client-side PDF tools do the same core jobs, compress, merge, rotate, split, delete and reorder pages, using JavaScript libraries that run in the page you have open. Nothing is uploaded, there is nothing to sign in to, and there is no free-use meter, because your own device is doing the work. For everyday document handling that covers the large majority of what people open Acrobat online for.
No. There is no sign-up, no sign-in and no watermark on the output.
No. Acrobat's web tools process files in Adobe's cloud; these tools run entirely in your browser so the file never leaves your device.
Heavy jobs like OCR or PDF editing with full layout control still belong to dedicated apps. For compressing, merging, rotating, splitting and page management, the browser tools cover it.