PDF tools that keep working when the connection does not

You are on a plane, or in a building whose guest wifi wants a login you do not have. There is a PDF on your laptop and you need to merge it, rotate it, or take three pages out of it. Online PDF tools generally stop being useful at that moment: the tool is on a server, not on your laptop, and your file has to travel there first. PDFCheetah is a set of offline PDF tools in the sense that matters on a plane — the work was never happening on a server, so losing the connection takes nothing away.

What offline means for a website

There is nothing to install and no offline mode to switch on. The first time you open PDFCheetah, your browser keeps a copy of the site's own files — the pages, the layout, and the code that reads and writes PDFs. That copy is roughly 1.5 MB and arrives in one piece on your first page view of any page. You do not need to open each tool while you still have a connection; the whole set is saved together or not at all.

After that, the tools run with no internet because they were never running anywhere else. Merging, splitting, compressing, rotating, reordering and deleting pages happen on your own device. Your document is not sent anywhere when you are online either, so going offline removes a step you were never using.

Two limits are worth knowing. The copy has to finish arriving: open the site on a weak connection, close the tab a second later, and nothing is kept. And a browser may clear stored site data to reclaim space, so a copy made months ago might not still be there. Neither failure announces itself, which is why the steps below end with a check you run yourself.

What works with no connection

• All six tools open and run. Merge, split, compress, organize, rotate and delete pages are saved together on your first page view, so none needs its own visit first.
• A whole job, from file to download. With the connection off you can select a PDF, look through the page previews, run the job and save the result. What that has been measured on is set out below.
• The pages around the tools. The home page, the tool list and the pricing page open too.

What has actually been measured is one tool. With the network disconnected, a fresh tab opened the Rotate page, loaded a PDF, ran the job and produced a downloaded file — in Chrome. The other five are saved by the same step at the same moment and should behave the same way, but that is reasoning from how the copy is written rather than a measured result.

What still needs a connection

• A device that has never opened PDFCheetah. Nothing is saved yet, so you get your browser's own error page. The first visit needs a connection.
• Safari, iPad and iPhone are unverified. Every offline check we run is run in Chrome. Nothing here tells us how offline use behaves in Safari or on an iPhone, so treat it as unknown rather than as working, and test it before you travel.
• Adding it to your home screen. Your browser may offer to install PDFCheetah as an app. That path is untested, so nothing here depends on it. The browser tab is what we check.
• Addresses with a ? in them. Sending a result straight from one tool into the next works while the page stays open. The address it leaves in the bar contains a ?, and reopening or reloading that address offline will not find it. Download the result and select it again in the next tool instead.
• The contact form. It sends a message to us, so it needs a connection.
• Version checks, and a small usage count. Offline, PDFCheetah cannot see whether a newer version exists, so you keep the one you have; a new version waits until you choose to reload, and never restarts a job under you. The anonymous count of which tools get opened also fails offline and is dropped. Nothing about your document is in it either way.

How to set it up before a flight

1. 1Open PDFCheetah on the device you will carry. The saved copy belongs to one browser on one device. Loading it on your phone does nothing for your laptop.
2. 2Leave the tab open for a few seconds. Roughly 1.5 MB has to arrive in one piece. On a slow connection this is the step that fails, without saying so.
3. 3Open a tool and read the offline line. Every tool page carries one. Once your browser is serving the page from its own copy it reads “Ready to work offline”. While it reads “Offline setup pending”, stay online and give it a moment.
4. 4Put the PDFs themselves on the device. A file sitting in cloud storage that has not been downloaded is not on your device, and no PDF tool can open what is not there.
5. 5Prove it before you leave. Turn off wifi, open a tool and run one small job. Thirty seconds on the ground is worth more than any sentence on this page.

Nothing here is a plan, a setting or a download. If PDFCheetah has loaded once in the browser you are holding, the tools are already on the device.