Laptop
Source: Unsplash

The PDF format reigns supreme whenever we talk about the most common document formats. It's used by businesses, students, and researchers alike to handle reports, contracts, presentations, and more. One reason for its popularity is its strong retention of quality across both text and visuals. It's also easy to share and view on a myriad of device types.

However, one of the biggest problems people face with PDF files is the large size of complex, multi-page documents. This makes them difficult to email and store, reducing their usability. This naturally leads to the question, 'How can I make a PDF file smaller without losing quality?' The good news is that there are plenty of ways to do this.

The Reasons for Large PDF Sizes

Before we get to the ways that can help you make your files smaller, let's look at why they get so large in the first place. Here are the three primary causes:

  • High-resolution images can dramatically increase file size. Many users don't realise this and embed very high-resolution visuals into their documents, even though that level of quality may not be necessary.
  • Embedding fonts into your PDF also increases the size. If a PDF includes entire font files for each of the typefaces you've used, its size can increase by megabytes very quickly.
  • Many PDF files also contain hidden data. This includes editing history, metadata, bookmarks, layers, and comments. For very long documents, this hidden data can add up.

Now that we know what causes files to become so heavy, let's take a look at how to compress a PDF quickly without much hassle.

Use Online Converters and Compressors

The quickest and easiest way to fix this issue is to use an online PDF converter like OnlyDoc, which handles everything automatically. Tools like this run in your browser and let you start editing documents without installing anything. Simply upload your document, select the compression level, and download the resulting file.

While different tools work in their own ways, you can usually choose from:

  • Light Compression: Minimal size reduction with nearly no quality loss.
  • Medium Compression: A balance between reduction and quality.
  • Strong Compression: Maximum size reduction, but with lower quality.

Compress Images Inside the PDF

You can reduce PDF file size within the document itself by compressing the images you're using. Here's how you can achieve a decent reduction:

  • Reducing your images' DPI values makes a big difference. Ensure your images are at 300 DPI if the document needs to be printed, or 150 DPI if it is intended for screen viewing. Anything above these numbers is often unnecessary and leads to larger file sizes.
  • Use efficient formats like JPEG for photographs. PNGs are more appropriate for graphics with transparent backgrounds or solid colors.
  • If you have scanned documents within your file, you can also compress them, as they behave like large images and contribute to the overall size.

Use Built-In Optimisation Tools

Several desktop PDF editors include built-in tools to reduce PDF file size without losing quality. You can use the option to reduce the size while exporting the file, or head to the advanced optimisation panel and use options such as:

  • Downsampling images;
  • Subsetting unused fonts;
  • Flattening transparency effects;
  • Removing embedded thumbnails;
  • Deleting comments.

These options work wonders for larger, multi-page documents, which often contain unnecessary data that increases file size.

Use the Right Colors

Many documents designed for printing use the CMYK color model. This is great for print, but it is not very efficient for digital distribution and storage. Converting the images in your file to RGB can often reduce PDF file size instantly while making the document more suitable for digital use. So, if you don't have to print your document, it's best to stick with RGB visuals for both size and efficiency.

Optimise Fonts

While the text in a document takes up very little space compared to visuals, the font files you use may add more weight to a file. Some tricks to optimise fonts include:

  • Using standard typefaces like Arial or Times New Roman.
  • Subsetting fonts so that the file contains only the characters you've used instead of embedding the whole font.
  • Removing duplicate font files.

Optimising fonts is particularly useful for long documents with extensive text. While the individual steps may seem small, they can help make your PDFs significantly smaller and easier to handle.

Conclusion

Knowing how to compress a PDF should be common knowledge for those who regularly work with documents, reports, and presentations. One of the main things to look out for is the quality of images embedded in your documents. Always remember to use a DPI that's appropriate for your needs, remove metadata, and convert colors to RGB unless you need to print. Taking simple steps like these is one of the best ways to reduce PDF file size, aside from using an online compressor.