Set a size limit
When the page opens, “Set target size” is already ticked. The defaults are a custom target size of 2 MB and the “Balanced” method. If your recipient specifies a different value, “Quick selection” offers 500 KB, 1 MB, 2 MB, 5 MB and 10 MB. With “Custom target size”, you enter a number yourself instead and choose the matching unit: KB, MB or MiB. Enter decimal values with a period, for example 0.25 MB or 1.5 MB; a decimal comma such as 1,5 is not accepted. Whether you need 500 KB, 2 MB or 3.5 MB doesn’t matter, because you set any limit in this same tool.
- Select your file with “Choose PDF”. It can be up to 50 MiB (52,428,800 bytes) in size. That is the limit for the file you put in, not your target.
- Leave “Set target size” ticked and set the limit, either with quick select or as a custom number with a unit.
- Choose the method: “Balanced”, “Smaller file” or “Lossless optimization”. What the three methods mean for readability is explained further down.
- Click “Reduce PDF to a target size”.
- Read the status message. “Target reached” shows both the result and the limit in bytes. “Target not reached” tells you that the file is still over the limit. You’ll also see the original and result sizes and the savings in bytes and percent.
- Page through every page in the comparison of original and result, especially the pages that matter to your recipient. Only download the result once it is complete and readable.
Processing takes place in your browser. The file isn’t uploaded to a processing server, and your original stays unchanged because the result is a new file. The tool doesn’t accept password-protected or encrypted PDFs. The same applies to digitally signed or certified documents and to damaged or unreadable files. How small a PDF can get depends on its content. You only know whether your limit was reached once you see the result.
Example: A form says “PDF, maximum 1 MB”. You choose 1 MB in quick select, and the tool checks against 1,000,000 bytes. If the form says “maximum 1 MiB” instead, you set a custom target size of 1 MiB, which is 1,048,576 bytes.
A maximum, not an exact file size
The target size is an upper limit. Here, “2 MB” means the result may be at most 2,000,000 bytes. A result of 1,400,000 bytes meets this target just as well as one of exactly 2,000,000 bytes. The tool doesn’t artificially pad a smaller file. Nor does it cut anything off or remove pages to hit a particular number.
In the end, what counts is what your recipient requires. If it says “up to 2 MB” or “maximum 2 MB”, a file of exactly 2,000,000 bytes also fits. If it says “under 2 MB” or “less than 2 MB”, a portal that checks strictly may reject exactly this file, even though the tool reports “Target reached”. In that case, a small buffer is worth it.
Example of a buffer: Instead of 2 MB, you enter a custom target size of 1.95 MB. The tool then checks against 1,950,000 bytes. A result that meets this limit is at least 50,000 bytes below 2,000,000 bytes. A tighter target can cost more image quality, so keep the buffer only as large as necessary.
Units and exact byte limits
Forms usually show a round number, but checks are done in bytes. In this tool, 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes and 1 MiB = 1,048,576 bytes, which is 1,024 × 1,024. The 500 KB quick select option therefore equals 500,000 bytes. 2 MB is 2,000,000 bytes, whereas 2 MiB is 2,097,152 bytes.
A calculation example with an assumed file of 2,050,000 bytes shows how much this matters. On a number line from smallest to largest, the values fall in this order:
- 2,000,000 bytes: limit at 2 MB
- 2,050,000 bytes: assumed example file
- 2,097,152 bytes: limit at 2 MiB
So the same file meets one limit but not the other. If a portal only says “MB” without explaining how it calculates, MB is the safe choice. It gives the smaller of the two limits, and anything below it also fits if the portal calculates in MiB. Only set MiB if the recipient explicitly says MiB or states that it calculates with 1,048,576 bytes per unit. With tight limits, don’t rely on rounded displays such as “2.0 MB”. Use the byte count in the status message instead.
Uneven values work too: 0.25 MB equals 250,000 bytes. If an entry results in a fraction of a byte, the tool rounds down. For example, 0.3 MiB = 314,572.8 bytes becomes a limit of 314,572 bytes. This means the limit is never more generous than what you entered. For other values, you can convert file sizes precisely before you enter the limit.
Understanding the three target outcomes
Finished processing doesn’t necessarily mean the limit was met. And a met limit doesn’t necessarily mean a portal will accept the file. There are three possible cases for the target size, but the tool shows only two messages: “Target reached” and “Target not reached”.
In the third case, the smaller file is still valid and ready to download. It just isn’t small enough for this limit. Your original file always stays untouched. The tool only offers a version as the result if it is actually smaller and passes the check. To pass, it must be a valid PDF. In addition, its page count, number of form fields, number of links and whether it has a document structure must match the original. This compares numbers and basic structure; it isn’t a functional test. You need to test the result yourself to see whether an important form field keeps its content or a link goes to the right destination. If no version meets these conditions, the tool shows your original unchanged as the result and offers it for download. An unchanged file can therefore mean two things: either it fits because the original was already small enough, or it is still over the limit.
Already under the limit
If the original is already at or under your limit, the tool doesn’t try to compress images further, because there’s no reason to sacrifice quality. Lossless optimization of the file structure may still run. The result is then the same size or slightly smaller, and the images aren’t intentionally changed.
This case also shows as “Target reached”. You can recognize it from the sizes shown: if the original size is already less than or equal to the limit, the file would have met the limit without any processing. You can then submit the original or, after comparing the pages, use the optimized copy.
Example: Your PDF is 1,900,000 bytes, and the form allows 2 MB. The file already fits. If you lower the target size to 1 MB just to be safe, you risk losing quality for no reason. For a requirement such as “under 2 MB”, a buffer such as 1.95 MB is enough. Also, don’t keep processing the same file with smaller and smaller limits. If in doubt, start again from the unchanged original.
If the PDF is still too large
If the tool reports “Target not reached”, you still have something to work with. Either the smaller valid version is ready to download or, if no smaller version was produced, your original is. The original itself always stays unchanged. Which next step makes sense depends on what your recipient allows.
- Try a different method: If you chose “Lossless optimization” or “Balanced”, “Smaller file” can compress images more heavily. This is only worth it if the result is still easy to read in the page comparison.
- Leave out pages that nobody really needs: You can drop blank pages, duplicate scans or attachments the recipient doesn’t ask for. With the right tool, you can remove unneeded pages while keeping the required pages in the document. Then select the saved file here again, because files aren’t passed automatically between the tools.
- Split into multiple files: This only makes sense if the portal explicitly allows multiple uploads. Then you can split the PDF and check each part here against your limit.
- Recreate the source: If the PDF comes from a scan, a new scan at a lower resolution may be smaller. A file from a word processor or graphics program can often be re-exported from that program with smaller images. Both happen outside this tool, because it has no setting for resolution or DPI.
If you try another program or service, check any smaller result carefully before you submit it. Some methods convert pages into images. Afterwards, you may no longer be able to select or search the text, and bookmarks or links may be missing. “Print to PDF” isn’t an equivalent lossless option either. Always keep your original.
Example with assumed requirements: A portal allows up to three files of at most 2 MB each. If your PDF is still over the limit even with “Smaller file”, you can split it into two parts and check each part here against 2 MB. If the same portal allows only a single file, splitting doesn’t help. Your remaining options are then removing unneeded pages or recreating the source.
Readability comes before aggressive reduction
The three methods differ in whether they affect image quality. “Lossless optimization” only reorganizes the file’s structure and doesn’t intentionally change images, but it isn’t always enough for a tight limit. “Balanced” and “Smaller file” also optimize the structure first and then recompress suitable images. Fine details can be lost in the process. So reducing size without losing quality is possible, just not for every limit. The page on general PDF compression explains how the methods work in principle.
That’s why you should page through every page in the comparison of original and result. Pay particular attention to small print, numbers and amounts, stamps and signatures in scans, and charts and fine lines. Reducing the size doesn’t remove pages, and the page count is even checked. But only you can judge whether the content is still easy to read. So only save a result in which everything important is clearly legible.
Example: With a scanned bank statement, every digit must stay unambiguous. If an 8 looks like a 3 after reduction, the result is unusable, even if it says “Target reached”.
File size is only one requirement
“Target reached” refers only to the size of this one file. A portal can still reject it if it has other rules, such as a maximum number of pages, an upper limit for all files combined, a limited number of uploads or specific file types. Each recipient sets its own rules. There is no universal limit for portals or authorities.
Example with assumed values: A portal allows 2 MB per file and 5 MB in total. Three PDFs of 1,900,000 bytes each meet the per-file limit, but together they come to 5,700,000 bytes. That is 700,000 bytes more than the 5,000,000 bytes allowed for all files combined. Using your portal’s requirements, you can check page and total limits before you upload.
When you send files by email, the size of the whole message may count instead of the file size. Attachments are often encoded with Base64 for sending. In that case, they grow by roughly a third. That turns 1,900,000 bytes into roughly 2.5 million bytes, plus line breaks, text and headers. How much of this actually counts depends on how your provider measures its limit. A PDF that shows “Target reached” for 2 MB here can therefore still exceed a limit of 2 MB per message. Before sending, you can estimate the email message size.