How to convert JPG to PDF without losing quality

Why images lose quality when they become a PDF

A JPG is already compressed. When a camera or phone saves a photo, it throws away detail the eye is unlikely to miss so that the file is small. That is fine once. The trouble starts when a picture is compressed again: each new round discards a little more, and edges start to look soft, flat areas get blotchy, and small text in a photographed document becomes hard to read.

Many online converters do exactly that. To keep their servers fast and their downloads small, they decode your photo, shrink it to a standard size and save it as a new, more heavily compressed JPG inside the PDF. You usually don't notice until you zoom in on a certificate, a receipt or a signature - and by then the original detail is gone from the PDF.

A PDF doesn't need to work that way. The format can hold a JPG image exactly as it was saved, without decoding it at all. A converter that does this gives you a PDF whose pictures are identical to your files. The only cost is that the PDF is about as large as your photos added together.

Step by step: JPG to PDF with no quality loss

1. Open JPG to PDF and select your photos, or drop them onto the box. On a phone you can pick them straight from your gallery. JPG, PNG and WebP are accepted - up to 20 images of up to 25 MB each.
2. Put the pages in order. On a computer you can drag the images; on any device the buttons on each image move it up or down, turn it, or remove it.
3. Under Image quality, keep Original. This is the setting that places JPG and PNG images in the PDF unchanged.
4. Choose the page size and margins (see the next section), then press Create PDF and download the file.

Everything happens in your browser: the photos are read from your device and the PDF is built there, so nothing is uploaded. That also means the PDF is ready as fast as your device can write it - there is no waiting for an upload, or for the result to download from a server.

Choosing page size, orientation and margins

These settings decide how the picture sits on the page. None of them changes the image itself.

• A4 or Letter gives a document that prints neatly and looks like a scanned page. A4 is standard in most countries; Letter in the United States and Canada. Each photo is scaled to fit the page, keeping its shape - nothing is cropped.
• Image size makes each page exactly the shape of its photo, with no white border. It suits photo albums, portfolios and screenshots, where a paper size doesn't matter.
• Orientation: Automatic turns each page to match its picture - landscape photos get landscape pages. Choose Portrait or Landscape only if every page must be the same way round.
• Margins: Small (about 7 mm) looks tidy when printed; None lets the picture fill the page; Large (about 14 mm) leaves room for hole punching or notes.

Placing a photo on a smaller page doesn't throw away its pixels. At Original quality the full image stays in the PDF and is displayed at the page size, so zooming in on screen still shows every detail.

When the PDF is too big: how much quality to give up

Keeping every pixel has one drawback: a PDF made of ten phone photos can easily be 30 MB or more, and many application forms and email services won't accept that. If you hit a limit, there are two sensible routes.

Lower the image quality when you create the PDF. Under Image quality, the other settings re-compress each picture and cap its size:

A photo of an A4 page at 2500 pixels on its longest side still prints at about 210 dots per inch - enough for clear text. That is why Medium is usually the best compromise for documents.

Or compress the finished PDF. Make the PDF at Original quality, then open it in Compress PDF and choose Target size - for example 2 MB. It tries the best quality first and steps down only as far as needed. This is the better route when you know the exact limit, because you don't have to guess which setting will fit.

Either way, keep your original photos. A smaller PDF is for sending; the originals are what you would use to make another version later.

Phone photos: sideways pictures and HEIC

Phones often save a photo sideways and add a small note saying which way is up. Some converters ignore that note and produce a PDF with pages turned on their side. SentrueFile reads it and turns each page the right way automatically; if a picture still looks wrong, use the rotate button on it before creating the PDF.

iPhones may save photos in HEIC format, which isn't supported yet. When you pick photos from the gallery, the iPhone usually hands them over as JPG anyway. To be sure, set Settings → Camera → Formats to Most Compatible so new photos are saved as JPG.

If you are photographing paper documents rather than converting existing pictures, Scan to PDF is made for that: it takes the photos with your camera, and its Document look turns the paper white and removes shadows, which also makes the PDF much smaller.

Common mistakes that cost quality

• Converting screenshots of photos. A screenshot of a photo is a new, lower-resolution image. Use the photo itself.
• Starting from images sent through a messaging app. Messaging apps shrink pictures heavily. Ask for the original file, or use the copy from the camera.
• Compressing twice. If you compress the photos first and then compress the PDF again, you pay twice. Do one or the other.
• Upscaling small images. Making a small picture fill a large page can't add detail; it only makes the softness bigger. Use the largest version you have.