How to Reduce the Size of a Scanned Document

Some scanned documents can be quite large. The size of scanned documents can be an issue if you need to send them to others through email or simply upload them online. The bigger the size of the scanned document, the longer it will take to upload them.

This can be a major issue for anyone needing to send an urgent file or need to meet a deadline. There are many ways to reduce the size of a scanned document and you will learn those ways today.

The benefits of lowering the file size go beyond increasing the time it will take you to upload these documents. When storing many different scanned documents on your computer, they can begin to bog your computer down and take up a lot of storage space.

Learning how to reduce the size of a scanned document will help not only you but your computer in the long run.

What Factors are At Play When It Comes to File Size

Now, the size of any scanned document can be affected by many different factors such as the quality of your scanner and the number of images located inside the document, but the file size can be reduced.

Before we can discuss that though, it’s important to understand why the file size of your document is as big as it is.

Scanner Type

Depending on the type of scanner that you purchased, your scanned documents can be extremely large, or normal sized. Each scanner is made differently. Getting a scanner that is well made will result in smaller sized files.

Your scanner will typically have different settings for your scan and these settings are what control how big or small the file size is. Keep in mind also that a better and higher priced scanner does not mean lower file size.

With some scanners, the quality of the image scanned is exceptional. This can also increase the file size and has to do with the DPI resolution your scanner is capable of scanning in.


The DPI setting of your scanner can cause the file size of your scanned document to increase. Take a scanner that has a DPI resolution of 4800×9200.

Those are rather large dimensions and as such a large file will be produced. This is not always a bad thing, but for those scanning a lot of documents at such high DPI, it can be bothersome to upload them online.

Of course, most scanners have the option to select different DPI before scanning and typically, the highest setting is not what you are aiming for when scanning. Sure, it has the best quality, but that does not mean the setting below it has bad quality.

That is important to keep in mind when scanning multiple documents that you would like to keep at a smaller file size.

Image Count

It only makes sense that the more images you have, the larger the file will be. Making sure to scan documents with a lower image count will drastically reduce the size of your PDF file.

Images take up a lot of space due to the nature of graphics. With all the different colors and data that goes into an image, the file cannot help being large.

If the documents you are scanning have too many images and there is nothing you can do about that, do not worry. There are ways to lower the file size even when the document has multiple images in it.

Size of the Document

This point may seem redundant, but the size of the document can affect the size of the PDF file. When discussing size, you should focus on the number of pages and elements on those pages.

The more pages you have in your document, the larger the file size will be. Looking further into it, the length and width of the document also come into play.

With bigger sized documents being scanned in, more data is being stored and this will increase the size of your PDF file.

How to Reduce the Size of a Scanned Document

Considering all the factors that go into increasing the file size of your PDF document, let’s look at how you can reduce the size. Lowering the number of images in the scanned documents you have can be hard if the documents cannot be altered before being scanned.

Therefore, we will discuss compression. Compressing an image will change the way it is rendered and thus lower the size of the image. To keep it simple, you should use a PDF software to achieve this.

With Adobe Acrobat, you can open and edit your PDF files. This will be the easiest way to lower the file size of your document. Once inside, you can edit the images located inside of your document.

Images hold a lot of the size that your document contains. Focusing on them is a great way to reduce the overall file size of your document.

If you are scanning a colored document and would like to reduce the file size, you should scan it in black and white. Black and white colors hold the least amount of data. Setting up your scanner or printer to only scan black and white is relatively simple with your scanner’s software.

There is also an option to lower the file size of your scanned PDF document in PDF software. This process is called optimization in Adobe Acrobat.

To reach these options, first, you will want to open your document up in Adobe Acrobat. There you can click on the “Document” tab at the top of your screen and click on “Optimize Scanned PDF”.

Here you will be given a set number of options. Each option can lower your file size. There is also a slider at the top of the dialog that you can use to make the file as small as possible or as high quality as possible (producing a larger file size).


Understanding how PDF files work and what makes them larger are smaller is the first step to reducing the size of your scanned documents. You should be focusing on the number of images located in your document, the DPI of your scanner and the image, the size of the document, and the type of scanner you have.

With options already available in Adobe Acrobat, if you are not able to control any of the reasons your file is so big then you can still reduce the size. Adobe Acrobat is made with PDF files in mind and altering them with the software is easy.

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