PDF is short for Portable Document Format and is a handy file format that offers many benefits. One of them is its size, relatively compact compared to other formats that contain text or images. This is possible thanks to the combination of several compression algorithms. But sometimes the file size is not small enough. Generally, additional compression of a PDF file is only possible through other programs..
The number of bytes in a PDF file does not increase due to the amount of text. The number of words is only significant from several hundred or thousands of pages. File size is much more influenced by high-resolution, deep-color images, diagrams, and graphics . Therefore, it is also problematic to convert a scanned document to a PDF - it is embedded as an image file, even if the scan is text only. With multiple scans, a dozen megabytes can be pooled quickly. The interactive forms and multimedia elements also contribute to increasing the overall size of the file.
Since the PDF format has no fixed page or storage restrictions, a large file is generally not a problem. However, there are many advantages to handling files as small as possible. First, the obvious: Shrinking a PDF saves hard drive space. When sending to an external data medium such as a USB memory, the transfer speed factor is also an important reason..
PDFs are also frequently sent as email attachments. This is because in a PDF document the format and fonts are fixed, which allows faithful reproduction of the original on all devices. This distinguishes them from Word files, for example. If you want to send text documents that are available as MSWord files by email, it makes sense to convert them to PDF beforehand. However, the free mailboxes of many email providers offer limited storage space and only allow you to send attachments between 4 and 35 megabytes.
Small PDF files also offer advantages as forms or resumes for online job applications in large companies, as many companies specify a strict megabyte limit for the documents that must be submitted..
When creating a PDF document, the ideal is to keep it as small as possible. The rule is simple: less information means a smaller file size. Photos should be compressed first. To do this effectively, image processing programs such as Photoshop or Gimp can be used.
The most important factor (besides dimensions and color depth) is the resolution of the image, which is specified in the unit dpi (dots per inch). Reducing the resolution from 600 to 300 dpi significantly decreases the size of a PDF from approximately 4.55 megabytes to 2.68 megabytes. When choosing the correct resolution, you should always keep in mind the purpose for which the PDF file was created. If it is only to be read on a computer screen, 72 to 96 dpi is sufficient. For a print or presentation it should not be reduced below 150 dpi - 300 dpi would be optimal.
If you already have a finished PDF or you are not the creator of the file, you will have to do a subsequent compression if you want the file size to be smaller. However, this is often the worst method, as a subsequent reduction in resolution is always detrimental to image quality, even if the loss of image information can be limited to the point of achieving a good result. There are several tools for posterior compression, which we will introduce and briefly explain below.
Of course, you can easily compress a PDF using WinZip. But this has the disadvantage that you have to unzip the ZIP file to open it again. Other tools allow you to reduce the size of a PDF directly. A precondition for doing this is that the document is not write-protected. Otherwise, you will need to remove this protection first.
Adobe, the company that originally developed the PDF format, also provides a tool for compressing PDF: Acrobat Pro DC (not to be confused with Acrobat Reader). After opening the document to edit, you can create an optimized PDF via "File"> "Save as (other)". In the menu that opens, you can check how much memory the individual elements (for example, fonts, images, bookmarks, forms, destinations, and comments) occupy by clicking the button in the upper right.
If you select the "Standard" option, Acrobat Pro will perform efficient compression to try to achieve the smallest file size possible, which will not result in a loss of too high quality. This is done by removing unused fonts, reducing image resolution, and removing unnecessary elements. If you want, you can also adjust the compression parameters yourself. For example, you can remove useless objects, discard user data, or adjust the transparency of images. The layman will have to experiment a bit, because too strict parameters can make printing images or using forms impossible.
In many cases, Mac users have already pre-installed an equivalent tool on their operating system: the preview application. Its functionality is almost the same as in Acrobat Pro: after opening a file, click "Export". In the pop-up window that opens, select the "PDF" format and set the filter to "Reduce file size." As with Acrobat Pro, the result is compressed using a standard algorithm.
Apart from these firmware tools, there are many other programs that can be found as freeware on the Internet. They are generally free, quick to install, and easy to use. A popular and practical example is PDF24 Creator.
Once installed, PDF24 works as a driver for a virtual printer. After opening a PDF with a reader or other program, click "Print." Now select "PDF24" as the printer in the list of available devices and confirm. The PDF document will not print, but the PDF24 launcher will open. Click "Compress PDF" to send it to the PDF24-Compress tool. Here all compression parameters can be adjusted and a storage location can be selected for the PDF file to be printed.
PDF24 Creator can also be used as a standalone program. With it, the file can be found on the computer or dragged to the interface. Like any other software, PDF24 Creator also offers some cool additional features such as a PDF viewer, various encryption methods, and the option to combine multiple PDF files into one large document or delete pages.
Examples of other free tools are BullZip PDF Printer and doPDF, which are also installed as printer drivers. These work (with slight differences) like PDF24, so the tool you use will depend on your personal preferences. However, you should be careful with lesser-known freeware or untrustworthy third-party programs: installation configurations can contain numerous ads and additional unwanted components.
Online tools can be an alternative to quickly reduce the size of PDF files. These can be accessed as web applications in the browser. Using the file search function or drag and drop, one or more PDF files can usually be loaded. The compression takes place in the website operator's cloud - you don't have to install a program or display great computer skills.
There are many of these free service providers on the Internet: good examples are SmallPDF, PDFCompressor, and PDF2GO. Like many free programs, they are very similar in use and features. Due to the numerous ad banners, these pages may seem somewhat confusing at first glance, but the ads are only used to fund the free offer.
As a general rule, these services can be used completely anonymously, so it is not necessary to enter any personal data. However, depending on the nature of a PDF, you should carefully consider whether you want to take a security risk and transfer the PDF file to another server instead of installing software on your own computer, as you are never one hundred percent safe from it. data theft on the Internet. In case of doubt, reading the information on data protection offers you the assurance that your own data is protected by the corresponding provider.
PDF24 claims to delete uploaded files from the server shortly afterwards. SmallPDF and PDFCompressor also guarantee permanent deletion of all data after one hour. PDF2GO, on the other hand, keeps compressed documents stored for 24 hours, so that the user can download a file multiple times, as explained by the provider. If this seems too uncertain with regard to data protection, one of the other online tools should be used.