Why is my PDF so big?

A woman compresses and resizes large PDF files on her laptop.

Not sure what to do with oversized PDFs? Learn how to compress and split your large PDFs to create seamless, high-quality files.

Wondering how to work with a large PDF file? If you’ve ever attempted to upload, file, save, or send a PDF and were shocked by its size, you’re not alone. There are a few distinct reasons that PDFs can sometimes be disproportionately large. There are also a few must-know tricks for resizing and compressing them without losing any quality.

Keep reading to learn more about PDFs and how you can maximize their efficiency without sending oversized files.

What creates a large PDF file?

PDFs are usually noticeably large when a few specific things happen. First, PDFs can be oversized because one or more fonts have been embedded and subset inside that specific PDF file. In fact, adding a single font to a PDF document can sometimes increase the file size substantially.

Second, images can also be a culprit. The overall resolution and bit-depth of an image can directly impact the overall file size — especially if you’re using color images with high resolution.

How to make large PDF files smaller.

The good news? Adjusting your PDF size is easy — there are a few different strategies to do so.

When you’re learning how to make large PDF files smaller, you can choose between the different strategies based on your needs. Compressing a PDF allows you to reduce its file size fast without compromising quality, while splitting a PDF into multiple, smaller files can help optimize your work.

Compress PDFs to make a large PDF file smaller.

Compressing a file reduces its size and allows for faster and more convenient sharing, uploading, and storing. You usually compress a file by allowing a program to scan the file and simplify its data.

Simplifying works by taking recurring data in the file and giving it a smaller identifier. Usually, this simplification doesn’t change the quality of the file. If there are large images or other multimedia in the file, however, it’s possible that the quality will change as the file size shrinks.

To compress a PDF for free online, use Acrobat online services:

  1. Using any browser, navigate to the online Compress PDF size tool.
  2. Using the “Select a file” button, upload the PDF you want to compress.
  3. Select a compression level — either high, medium, or low, based on your needs.
  4. Download your compressed PDF.

Now you have a smaller, good-quality PDF that you can send faster and store easier.

Wondering how to compress a large PDF file into other sizes yourself, or on other devices? These guides may help:

Split a large PDF file to make it smaller.

Splitting a PDF is different from compressing a PDF, because it doesn’t change the size of the file and doesn’t change the way the data in the file is configured. Because it doesn’t change the file on that level, it never compromises the file quality. It simply cuts the PDF into multiple, smaller pieces that are easier to manage. A smaller PDF can be sent and uploaded faster.

Splitting a PDF is a great option if you only need to send part of the file, or if you don’t mind sending multiple PDFs instead of just one large PDF file.

To split a large PDF file online, use Acrobat online services:

  1. Using any browser, navigate to the online Split a PDF tool.
  2. Upload the PDF you want to split, either using the “Select a file” button or dragging and dropping it into the box.
  3. Sign in.
  4. Select the dotted lines between pages to specify where you want your file split.
  5. Click Save and download your (multiple) PDFs.

Now you have multiple PDF files that will send much faster. You can also use Adobe Acrobat to split a PDF.

How to prevent a large PDF file.

You might be wondering, “How did my PDF get so large in the first place?” There are actually a few ways you can prevent a large PDF file as you’re creating one.

One of the simplest things you can do is use the Save As button instead of the Save button. It turns out that the data takes up less space when it writes an entirely new file as opposed to adding changes to an already existing file. When you Save As, it gives you a new file.

Fonts can be one of the bulkiest parts of a file, so if you’re using a new font, go under options and select the option to subset your font. This will make it so that it’s not the entire font that’s saved on your PDF file, but just the characters you use.

Even bulkier than fonts are pictures. While images can play a key role in your PDF, it can cut back on file size to evaluate whether you need them to be the highest quality available. Consider compressing your images before you put them in your PDF.

A couple of other tips include using the RGB color space if you’re not going to print and generally evaluating your file for unnecessary additions and removing those. If you’re proactive, you won’t have to spend too much time compressing your PDFs.

How to email large PDF files.

You might find your PDF too large to email, but you’re still skeptical about making it smaller. If you don’t want to make your PDF smaller by compressing or splitting it, you can always upload it to cloud storage and then just email a link to your PDF. While this is a simple solution, keep in mind that your large PDF file will be taking up room in your cloud storage and still might be a little bit slower to open and view because of its size.

Don’t let large PDF files stand in your way.

The size of your PDFs should never get in the way of your projects — don’t let large files trip up your creative process.

Discover what more you can with Adobe Acrobat and Acrobat online services to convert, share, and send PDFs.