Ask questions about a PDF without paying for a subscription
Our free plan reads PDFs: four models, one file per message, three a day. What that covers, how to ask well, and the point where it stops.
Ask questions about a PDF without paying for a subscription
The flat came with an air source heat pump and no explanation of how to live with it. What it did come with was a 46-page PDF, the installation and user manual, buried in the folder of documents the letting agent emailed over in August. It is now the first properly cold week. The radiators are lukewarm, and the controller on the hallway wall is showing E9.
You rarely need every page of a 46-page manual. You read about four sentences of it, the four that answer the question in front of you, and the whole difficulty is finding them. Twenty minutes of scrolling through a PDF viewer looking for a table of error codes is exactly the kind of job an AI chat handles well, and it is a job you can do on our free plan without putting a card in.
There is a catch, and it is worth two minutes of your attention before you drag the file in.
Pick the model before you attach the file
On a paid plan you can attach and think later. 25 of our 60 models take a PDF straight through, so whatever you had selected is probably fine.
The free plan works the other way round. It carries 21 models, and four of them read PDFs: GPT-5.4 Nano from OpenAI, and three Gemini Flash Lite entries from Google, versions 3.5, 3.1 and 2.5. That is the whole list. If you happen to be sitting in one of the other seventeen when you drag the manual in, the file will not attach, and you will see this instead:
This model doesn't support PDF uploads. Switch to a model that accepts PDFs.
That check runs on your own device, before anything is sent anywhere, which is quietly useful on a free plan: a refused file costs you nothing from your daily allowance. Switch model, drag it in again, and you are moving.
So the habit to build is small and slightly backwards. Choose the model, then open the file picker.
Three uploads a day is the number that shapes everything
The free limits are worth knowing exactly, because they are lopsided in a way you can use. One attachment per message, up to 10MB. Three uploads a day. Fifty messages every 24 hours.
Messages are plentiful. Uploads are the scarce thing. Once the manual is in the conversation it stays part of that conversation, so every follow-up you ask about it comes out of the generous budget rather than the tight one. The move on free is to upload once and then stay in that thread and interrogate it properly, rather than starting a clean chat every time a new question occurs to you and attaching the same file again, which in the phone app spends another of your three uploads.
The heat pump manual is about 2MB of ordinary text, which is typical. Files only get near 10MB when they are full of photographs or scanned pages, which is its own problem, and we will come back to it.
What a good question to a manual looks like
Start with the thing that is actually happening. "The controller is showing E9 and the radiators are barely warm. What does this manual say E9 means, and what does it tell me to do about it?"
Then verify before you act on any of it. "Which page is that on, and quote the line that says so." A model that has genuinely read the pages will give you a page number and a sentence you can go and look at. One that is filling in from general knowledge about heat pumps will get vague at exactly this point, and vagueness here is your signal to stop trusting the answer rather than to ask again more politely.
Then keep going, because the file is already there. "The manual keeps referring to weather compensation. Explain what it means in this manual's own terms and tell me which setting on this unit controls it." Or: "I am away for a week from Friday. What does the manual recommend I set, and what does it warn against leaving on?"
The pattern underneath all of those is that each one names the document. "What does the manual say about E9" and "what does E9 mean" are two different questions, and only the first one is anchored to the pages you uploaded. The second invites the model to answer from everything it has ever read about heat pumps, which is where confidently wrong answers come from. Keep pointing at the file and the answers stay checkable.
This is also why asking beats summarizing for a document like this one. A summary of a manual is a table of contents you already have. What you want is the four sentences.
What our extractor cannot read
Here is the failure worth planning around. We extract text from your PDF, and a PDF that is really a stack of photographs of paper has none. Our extractor is blunt about it internally, reporting that the file "appears to be image-based or has minimal text content". A scan of up to 20 pages is then transcribed for signed-in accounts, and the model is told the text may contain recognition errors; a fault code is exactly what a transcript can misread. Past 20 pages that step is skipped, and what a model does with pages we could not read is not something we would ask you to rely on.
On a plan with three uploads a day you would rather know before you spend one. The check takes five seconds. Open the PDF in whatever viewer you already have, bring up its find box, and type a word you can plainly see on the page in front of you. A viewer that jumps straight to it is reading real text, and so will we. A viewer that reports no results is looking at a photograph, and we will be reading a transcript at best.
For a manual the fix is easy and better than the original anyway: nearly every manufacturer publishes the same document on its own support site, and that version will be proper text. For something you cannot re-download, type the paragraph you care about into the message by hand and ask about it that way. It is a clumsy fix that works, and it costs you no upload at all.
Where the free plan stops being enough
It stops at a point you can see coming, which is the honest thing about it.
It stops when your question spans two documents. One attachment per message is the free rule, so the moment you want to hold the manual next to the service record the landlord sent, or a quote next to the invoice that followed it, you are asking for something the free plan does not do. Pro allows two files per message at 20MB each, or files kept in a folder for every chat inside it.
It stops if your source is not a PDF. Word documents, spreadsheets and text files are all read here, and all of them sit behind Pro. On free, PDFs and images are what you get.
It stops on day four of an ongoing job, when three uploads a day starts to feel like rationing. And it stops when the document is genuinely dense, because the four models that read PDFs on the free plan are the quick ones, and if their reading of a technical appendix comes back thin, the models you would reach for next are on the paid side. Roughly how much a model can hold in view at once matters here too, and we wrote about that in what is a context window.
So yes, we sell a subscription. Pro is $20.99 a month. The free plan does one document at a time and does it properly, and the day your work involves several documents at once is the day you are buying something.
A word on where the file goes
We do not train on your conversations. Some providers may, depending on which model you pick, and the models where we know of a difference carry a notice on their info card. None of the four free PDF readers does, which tells you nothing either way, so think before you upload anything you would not email to a stranger.
Is the free plan enough for this?
For the heat pump manual, comfortably. For most of what is actually sitting on a normal laptop, comfortably: an appliance guide, a warranty, a 30-page information pack from a school, a statement, a form that came back from an office with instructions attached. Anything with real text in it, under 10MB, that you could read in an afternoon if you had the afternoon. Three of those a day.
What it will not carry is research, or work where documents arrive in sets and only mean something next to each other. Somewhere around the second document you need open at the same time, the free plan quietly turns into a demonstration of the paid one. That is a fair place for a line to sit, and we would rather tell you where it is than let you find it at eleven at night in front of a cold radiator.