Why is my PDF larger than the photos it contains?

It should not be by much. If it is, the images were re-encoded at a higher quality than the source, or a lossless format such as PNG was embedded where the source was a compact JPEG.

What is HEIC and why will nothing open it?

HEIC is the container Apple devices use by default. It stores roughly the same visual quality as JPEG in about half the space, but support outside Apple's ecosystem is still uneven, which is why converting to PDF is often the simplest way to share.

Turning photos and images into a proper PDF

Each image becomes one page, so the decisions that matter are page size, orientation and how much resolution you keep.

Image-to-PDF is a packaging operation: each image becomes one page. The conversion itself is straightforward, so the quality of the result comes down to three decisions.

Decision 1: page size

An image has pixel dimensions and no inherent physical size. Placing it on a page requires choosing one.

Fitting each image to a standard A4 or Letter page gives you a document that prints predictably and looks like a document. Sizing each page to the image's own aspect ratio gives you a file with no white borders but with pages of varying dimensions, which looks odd on screen and awkward on a printer.

For anything that represents paper — receipts, forms, signed sheets, scanned letters — use a standard page size. For a photo portfolio where borders would be intrusive, matching the image is defensible.

Decision 2: orientation

Photos carry an EXIF orientation flag: the sensor recorded the image one way and a tag says how to rotate it for display. Well-behaved converters read that flag. Some pipelines strip EXIF before conversion, which is how you end up with a PDF of sideways pages from photos that looked correct in your gallery.

Check the first few pages of the output. If pages are rotated, fix them with Rotate PDF rather than re-shooting.

Decision 3: resolution and quality

A modern phone photo is 12 megapixels or more. Placed on an A4 page that is roughly 900 DPI — far beyond what any printer will reproduce and several times what any screen can show.

Keeping all of it makes each page several megabytes. Twenty pages and the file is too large to email. Downsampling to around 200–300 DPI for the page size loses nothing you can see on paper and cuts the file dramatically. If your converter keeps full resolution, run Compress PDF afterwards and check the result at 100% zoom.

The exception is a document you intend to OCR: recognition benefits from detail, so keep 300 DPI at the page size and compress only the distribution copy.

Format-specific notes

JPEG is the common case. JPG to PDF can embed the existing JPEG data directly, so there is no second lossy step and no quality loss at all.

PNG is lossless and typically large. PNG to PDF is the right tool for screenshots and diagrams, where the crisp edges are the point. Expect a bigger file than the equivalent JPEG-based document.

HEIC is what iPhones produce by default. HEIC to PDF decodes it in the browser and lays the photos out as pages, avoiding a separate conversion step. This is the fastest route from a camera roll to a shareable document.

WebP appears increasingly from web sources and screenshot tools; WebP to PDF handles it the same way.

If the images are documents, scan rather than photograph

Photographing a sheet of paper with the camera app captures the whole scene: uneven lighting, a shadow from your hand, the desk around the edges, and perspective distortion from holding the phone at an angle.

The document scanner is built for this case — a fixed capture ratio and processing tuned for paper rather than for photographs. The output is more legible, more consistent between pages, and considerably smaller. The full sequence is in combining scanned documents.

Order matters

Images are laid out in the order the tool lists them, which is the order the browser handed them over — not necessarily the order you expect. Confirm and reorder before converting; a 30-page PDF of shuffled receipts is not worth re-doing.