Images—
PageA4
Lowest dpi—
Size—
Every converter asks the same three questions — page size, orientation, margin — and none of them answers the one that decides whether the result is usable: what resolution does the picture actually print at once it is laid on that page? A 960-pixel screenshot stretched across an A4 sheet is reproduced at 90 dpi, which looks fine on a monitor and visibly soft on paper. This tool reports that number for every image before you download, and embeds JPEGs byte for byte so nothing is recompressed on the way in.
Step by step
01Add the images
Drop them anywhere on the page. JPEG and PNG go in as they are; WebP, AVIF, GIF, and HEIC have no PDF representation and are redrawn as PNG, which is flagged on the image it happened to.
02Choose the page
A4, Letter, A3, A5 — or Fit, which makes each page exactly the image's own shape. Auto orientation turns the page for a wide image rather than shrinking it to fit a portrait one.
03Read the resolution
Each row carries the effective dpi: the image's pixel width divided by the physical width it is drawn at. The lowest one is the verdict for the document.
04Check the real page, then download
The preview is the first page rasterised out of the finished PDF, not the source image dropped into a page-shaped box — so the margin, the crop, and the background colour are the ones you will get.
A worked conversion
The two sample images this tool opens with, on A4 with a 36-point margin and automatic orientation. Both are wide, so both get a landscape page.
Given
What each image is actually reproduced at
A4 landscape 841.89 × 595.28 pt
minus a 36 pt margin 769.89 × 523.28 pt = 10.69 × 7.27 inches
photo 1600 px ÷ 9.69 in = 165 dpi fine on an office printer
screenshot 960 px ÷ 10.69 in = 90 dpi visibly soft on paper
to reach 300 dpi at 10.69 inches you would need 3,207 pixelsThe picture did not change; the page it was stretched across did. A bigger page is a lower resolution, which is the opposite of most people's intuition and is why choosing A3 to 'give the image more room' makes the print worse — the same 62 dpi the tool reports when you try it here. The Fit page size lands on exactly 72 dpi every time, because it makes one pixel one point and a point is one seventy-second of an inch; that is the right choice for a screenshot destined for a screen and the wrong one for anything going to a printer. If a number has to be memorised, it is this: 300 dpi is commercial print, 150 is where an office laser stops showing softness, and below that the paper shows you what the monitor was hiding.
Before you convert
Resolution is a property of the pairing, not the file
An image has pixels; a page has inches. Dividing one by the other gives the dpi, and it changes every time you change the page size or the margin. That is why no converter can put a quality label on your file at upload time, and why this one computes it against the layout you actually chose.
A PDF can carry JPEG and PNG, and nothing else
Those two formats are part of the PDF specification, so their bytes are embedded verbatim — a photo goes in exactly as it came off the camera, with no second round of lossy compression. WebP, AVIF, GIF, and HEIC are not in the specification at all and have to be redrawn as PNG first, which keeps every pixel but discards the original file's compression.
A bigger page makes the image worse
Scaling a fixed number of pixels across more paper spreads them thinner. Choosing A3 for a photo that was borderline on A4 does not improve it; it moves it from 165 dpi to 62. The only ways up are a bigger source image or a smaller page.
Fill the page always crops
Fitting inside the page keeps the whole image and leaves paper showing where the shapes differ; filling the page scales up until nothing shows and loses whatever hangs over the edges. The percentage lost is reported per image, because a 30% crop through the top of a document is not a styling choice.
Fit means exactly 72 dpi
The Fit page size makes each page the image's pixel dimensions in points, and a point is one seventy-second of an inch — so the page is the picture at 72 dpi by construction. It is the right answer for screenshots, diagrams, and anything that will only ever be looked at on a screen, and the wrong one for print.
The images people convert are the ones not to upload
Photographed contracts, passport scans, receipts for an expense claim, medical letters. Converting them means handing the image to whichever service is first in the search results; doing it in the page means the file is read from disk and written back without a request being made.
The judgement call
Where the document is going decides this, not what the images are.
Screenshots for a bug report or a wiki
Fit
The page becomes the shape of the picture, nothing is scaled, and 72 dpi is exactly right for something only ever read on a screen.
Photographed documents to email as one file
A4 or Letter, fit inside
A consistent page makes it read as a document, and fitting inside guarantees nothing at the edges is cropped away.
Anything going to a printer
The smallest page that holds it
Resolution goes up as the page comes down. Check the reported dpi clears 150 before committing, and 300 if it is being printed properly.
A photo book or a poster
Fill the page
Edge-to-edge is the point, and the crop percentage tells you how much you are giving up for it.
The dpi reads under 100 and cannot be improved
Use a smaller page
Upscaling the image invents detail rather than adding it. A5 instead of A4 doubles the dpi for free.
Reference
FAQ
Use a converter that embeds the JPEG rather than re-encoding it. JPEG is part of the PDF specification, so its bytes can be copied straight into the document with no second lossy pass — which is what the Tinapps JPG to PDF tool does, and it says on each row whether an image was embedded as-is or had to be redrawn.
Divide the image's pixel width by the width in inches it is drawn at on the page. A 960-pixel screenshot across a 10.7-inch A4 landscape page is 90 dpi; the same image on A5 would be about double that. The Tinapps JPG to PDF tool computes this for every image against the page and margin you chose, because the number depends on the layout rather than on the file.
Almost always because it is being drawn larger than its pixel count supports. Screens show around 96 pixels per inch and print needs 150 to 300, so an image that looks sharp in a browser can be soft on paper at the same physical size. Choosing a smaller page raises the effective resolution; enlarging the image does not, because upscaling invents detail rather than recovering it.
Yes, but they cannot be embedded directly — neither format exists in the PDF specification, so they have to be rasterised to PNG first. The Tinapps JPG to PDF tool does this in the browser and marks the affected images as re-encoded, so you know which pages went through a conversion and which are the original bytes.
With most converters, yes. The Tinapps JPG to PDF tool decodes the images and writes the document inside the browser, so nothing is sent anywhere — which matters because the images people convert are usually photographed contracts, ID scans, and receipts.
Add them all at once and order them. In the Tinapps JPG to PDF tool each image becomes its own page, the rows can be moved with the arrows or sorted by file name in one click, and there is no limit on how many you add because nothing is uploaded.
Fit the page when the PDF will only be read on a screen: each page becomes exactly the image's shape, nothing is scaled, and the result is 72 dpi by construction. Choose A4 or Letter when it will be printed or filed alongside other documents, where a consistent page size is what makes it read as a document.
Barely, if the images are JPEGs. The bytes are copied in unchanged and the PDF adds a few hundred bytes of structure per page, so the document weighs roughly what the images did. A large jump means something was re-encoded — which the Tinapps JPG to PDF tool reports rather than leaving you to infer from the size.
The images are decoded and written into the PDF entirely in your browser. Nothing is uploaded, and the document exists only as the file you download.
Keep going
Merge PDF
Combine the converted images with the rest of the paperwork.
Image resizer
Raise the pixel count before the page pushes the dpi down.
Image compressor
Bring the photos down before they become a 40 MB document.
Paper sizes
What A4, A3, and Letter measure, and how the dpi moves between them.