PDF work on a phone, without an app

On iPhone, PDFs live in the Files app, and any file picker on a web page can reach them — including iCloud Drive, and Dropbox or Google Drive if those apps are installed. On Android the picker reaches Downloads, Drive and anything else that has registered as a storage provider.

The result of a job downloads back to the same place. On iOS that is Files, where it can be shared straight into Mail or Messages; on Android it is the Downloads folder and the usual share sheet.

That is the whole workflow. There is no upload and no account, so nothing has to be transferred between a phone and a desktop to get work done.

A phone has a far better scanner than most offices own. Capturing pages in the browser opens the rear camera directly, and each page can be cropped by dragging its corners and cleaned up so the paper reads white rather than grey.

The corners are dragged by hand deliberately — automatic edge detection is exactly the feature that silently crops the last line off a page and produces a document that looks perfect and is missing something.

The result is a normal PDF. Run it through recognition afterwards if you need the text to be searchable.

Memory is the real limit, and it is much lower than on a laptop. Mobile browsers give a tab a smaller allowance and are quicker to discard one in the background, so a very large document — hundreds of pages of high-resolution scans — can fail on a phone and succeed on a desktop.

Two practical consequences. Split a very large job into parts rather than fighting it. And keep the tab in the foreground while something is processing; switching to another app can have the browser reclaim the tab mid-job.

Recognition is the heaviest thing here and the slowest on a phone, because it works page by page and each page is real computation. It works — it is just a job to start and leave running rather than wait on.

Once the page has loaded once, the tools and their processing engines are stored on the device. After that they work with no connection at all — on a flight, on the underground, or anywhere the signal has gone.

That is also the strongest possible demonstration that nothing is being uploaded: a tool that works with the aeroplane mode on is not sending your document anywhere.

Both platforms can save a web page to the home screen, where it opens without browser chrome and behaves like an app — but without an install, an account or access to anything on the device beyond the files you choose.

On iPhone that is Share, then Add to Home Screen. On Android it is the browser menu, then Install or Add to Home screen.

A photograph of a page and a scan of a page are different things, and the difference is visible to everybody who receives them. A photograph is a rectangle of desk with a page somewhere in it, lit from one side, taken at an angle. A scan is the page, square, on white.

The gap between those two is cropping and a levels adjustment, both of which take a couple of seconds per page in the browser. It is the single biggest improvement available to anybody sending documents from a phone, and it costs nothing.

If the document has to be searchable — a receipt you will look for later, a contract you will need to quote from — run recognition over it afterwards. On a phone this is the slowest thing here, so start it and put the phone down rather than watching it.