How to Turn Photos into One PDF for Applications and Forms (JPG to PDF Tips)
Combining photos into one PDF is easy. Getting a PDF small enough for an upload portal, with sensibly sized pages, takes one extra step before you upload -- here's what our tests showed.
How our JPG to PDF tool builds the PDF
Our JPG to PDF tool puts each photo on its own page, in the order of the file list. Files are added to the end of the list each time you choose more, and each one has a Remove button, so the easiest way to get the order right is to add the photos one at a time.
Your JPGs are placed into the PDF exactly as uploaded, byte for byte. There is no second round of compression, so no quality is lost -- but it also means the PDF ends up about the same size as all your photos added together. In our test, three images totalling 14,124 KB produced a 14,126 KB PDF.
Photos taken with the phone held upright are shown upright. Phones often store such photos sideways with a tag telling viewers how to turn them, and our tool follows that tag: our sideways-stored test photo was set to display upright in the PDF.
Why the pages can come out enormous
The page size of each PDF page is worked out from the photo's pixel count and its dpi label (dots per inch) -- the setting that says how big the picture should be when printed. Photos from cameras and phones are often labelled 72 dpi, or have no dpi label at all.
In our test, a 12-megapixel photo (4032 x 3024 pixels) labelled 72 dpi became a page of 56 x 42 inches -- about 142 x 107 cm, far larger than A4. The same photo with no dpi label became a 42 x 31.5 inch page. A scan saved at 300 dpi by contrast came out at its true size, 8.3 x 11.7 inches (A4).
Most people won't notice, because PDF readers zoom to fit the screen. But a reviewer who prints the file, or a portal that checks page size, may.
Why Compress PDF may not shrink a photo PDF
This surprised us. We combined two realistic phone photos (about 2.7 MB each) into a 5,456 KB PDF and ran it through Compress PDF at all three levels. The file stayed at 5,456 KB every time.
The reason is the page size. Compression reduces image resolution in dots per inch, and on a 56-inch-wide page a 4032-pixel photo is only 72 dpi -- already below every threshold, so there is nothing for the compressor to reduce. Our Compress PDF tool gives you the original back when it can't make the file smaller.
When we labelled one of the same photos 300 dpi, compression worked as expected: the 2,726 KB one-photo PDF shrank to 319 KB on eBook and 116 KB on Screen.
The reliable fix: resize the photos first
For applications and forms, a photo doesn't need 12 megapixels. Resizing each photo before converting makes the PDF smaller and the pages more sensible at the same time.
In our test, resizing a 12-megapixel photo to 1600 x 1200 pixels at JPEG quality 85 cut it to 359 KB, and a PDF of two such photos was 720 KB -- down from 5,456 KB. At 2000 x 1500 pixels each photo was 526 KB, which still keeps small print on a document readable.
On Windows, open the photo in Paint, choose Resize, select Pixels and enter a width, then save a copy. On a Mac, open it in Preview and use Tools > Adjust Size. Many phone gallery and sharing apps also offer a smaller size option.
| What we did | PDF size |
|---|---|
| Original 12-megapixel photos (about 2.7 MB each) | 5,456 KB |
| Same PDF through Compress PDF (any level) | 5,456 KB - not reduced |
| Photos resized to 2000 x 1500 first | About 1,050 KB (526 KB per photo) |
| Photos resized to 1600 x 1200, quality 85, first | 720 KB |
The 2000 x 1500 PDF size is estimated from the measured photo sizes, since JPG to PDF keeps each JPG unchanged.
Tips for application and form uploads
Read the portal's rules first: maximum file size, whether it wants one PDF or separate files, and whether it asks for a particular page size.
Photograph documents flat, in good light, with the whole page in frame, and crop away the background before converting.
Add pages in the order the form asks for -- for example ID front, ID back, then certificates -- adding one photo at a time.
Our JPG to PDF tool accepts JPG files. For PNG screenshots, use PNG to PDF, then join the two PDFs with Merge PDF.
Open the finished PDF and check every page is upright, readable and in order before you submit. Your photos and the PDF are deleted from our server as soon as your download is ready.