Merge PDF
Merge, split or compress: what happens to your PDF's text
Three tools, two very different operations. Merging and splitting copy pages exactly as they are; compressing redraws every page as an image. Which one you pick decides whether the text stays searchable.
Most online PDF tools upload your document to a server and hand back a result. These three do the whole job inside your browser tab: pdf-lib reads documents and writes new ones, and pdf.js draws pages when a picture is needed. Both load the first time a tool runs, and no page of any PDF leaves your device.
Merge and split copy pages, they do not redraw them
Merging copies the pages of every input document into one new file. Nothing is re-rendered or re-compressed: each page arrives exactly as it was, at its own size, so a pile of mixed orientations stays right way up and print-ready. Splitting works the same way in reverse. The pages you pick are copied into new files, so text stays text and images keep their original resolution.
What does not come along
A copy of a page is not a copy of the whole document. A few things belong to the document, not the page, and they are left behind.
- Interactive form fields: the values stay drawn on the page, but the fields stop being fillable.
- Bookmarks: document-wide bookmarks are not copied, by merge or by split.
- Links that leave the extracted pages: a link between pages survives where its target is inside the same part; a link pointing outside is left as it is and may lead nowhere in the new file.
- Password protection: a locked file is refused with a clear message. Remove the password in a reader first, then use the unlocked copy.
Compress is a different operation
Compressing does not copy anything. Every page is rendered the way a viewer would draw it, encoded as a JPEG and placed into a fresh PDF 1.4 document, one image per page, at the page's own size. That shrinks scans and photo exports by 70–90 % in the typical case, because the original images are resampled at screen resolution instead of camera resolution.
The price is stated on the tool's page before you run it: text stops being text. A compressed document cannot be selected, searched or copied from, and small print softens at low resolutions.
| Tool | What it does to the pages | Text afterwards | Typical use |
|---|---|---|---|
| Merge PDF | Copies every page, in the order you set | Stays selectable | One document from several scans or chapters |
| Split PDF | Copies the pages you pick, by range or one file per page | Stays selectable | Extract one page or one section |
| Compress PDF | Redraws every page as a JPEG | Becomes a picture | Getting under an email or portal size limit |
Resolution and limits
Compress asks for a resolution. Use 110 dpi for screen reading and email, 150 dpi when the document may be printed, and 72 dpi for slides and forms where every kilobyte counts. The lower the resolution, the smaller the file and the softer the page. If the redrawn file would be barely smaller than the original, the tool says the document is already compact instead of handing you a pointless copy.
- Merge: up to 20 files per run, 200 MB each.
- Split: any page ranges, or every page in its own file for documents of up to 200 pages; 200 MB per file.
- Compress: documents of up to 300 pages, 200 MB per file.
Choosing in practice
- You need one document made of several: merge.
- You need only some pages of a document: split.
- You need a smaller file and the text does not have to stay text: compress, and keep the original.
- You need to put one PDF in the middle of another: split the document you are inserting into at the right page, then merge the three pieces in the order you want.
Every output is an ordinary PDF, so the tools chain: the result of a merge can be split, and the result of a split can be merged again. Do the compressing last, because everything after it copies pictures, not text.
Questions
Can I make a PDF smaller and keep the text selectable?
Not with these tools. Merge and split copy pages untouched, so they cannot shrink a file below the size of its parts, and compress turns each page into a picture. If the text matters, keep the original next to the compressed copy.
Why does the compressor say my PDF is already compact?
A text-only PDF that was generated cleanly has little to give. When the redrawn version would be barely smaller than the original, the tool says so instead of returning a copy that gained nothing.
In which order should I use the tools?
Merge or split first, compress last. Compressing first turns every page into a picture, and any later merge or split would then copy pictures instead of text.
Are my documents uploaded anywhere?
No. The files are read and rewritten in your browser tab, nothing is sent to a server, and the tools keep working offline once the page has loaded.