Add attachments
Carry other files inside a PDF.
This tool runs entirely in your browser. Your file is never uploaded, and you can verify that in your browser's network tab. Verify it yourself: open your browser's network tab and watch. You will see one small request asking whether you have tasks left - a tool name and a hash, never the file.
What this does
A PDF can carry other files inside it, the way an email carries attachments. This adds them: the first PDF you drop is the carrier, and every other file you add is embedded into it. The pages are untouched - an attachment is stored beside the document's content, listed in the reader's attachments panel, and extracted with a double-click.
Reach for it when the document and its evidence should not be separated: the spreadsheet behind a report's figures, the raw measurements behind a chart, the signed original behind a scan, a set of photographs behind an inspection sheet. It is also a way to get one file past a system that accepts a PDF and nothing else.
How it works
- Drop the carrier PDF onto this page first, then add the files to embed - up to 20 in one pass.
- Give any attachment a description if its file name does not explain it. Readers show that line next to the file.
- Decide whether to keep the attachments already in the document or clear them first.
- Press Attach.
- Open the result and check the attachments panel before you send it - the pane is called Attachments in Acrobat and Preview, and it is where the recipient will look.
Attached files are stored whole and compressed, so a 4 MB spreadsheet makes the PDF roughly 4 MB larger - less if it compresses well, never smaller. That is the honest trade for having one file instead of two, and it is worth checking against whatever mailbox limit the document has to pass. Compress PDF shrinks the pages; it will not shrink what you have embedded.
Each embedded file is written with its uncompressed size and modification date, so Acrobat's panel shows real numbers rather than "0 bytes, unknown date", and with both an old-style and a Unicode name so an accent or a non-Latin character in a file name survives. Each one is also registered as an associated file, which is what makes a PDF 2.0 or PDF/A-3 reader treat it as belonging to the document rather than as loose baggage.
The list of embedded files is rewritten in sorted order every time rather than appended to. The format requires that order, and readers that search the list rather than walking it return nothing at all from an unsorted one - which is how an attachment ends up in the file and invisible in the reader. A name that clashes with an existing attachment becomes "report (2).pdf" rather than replacing it silently.
This is also, plainly, how a PDF becomes a delivery mechanism for something unpleasant. The same feature is what Sanitise PDF exists to strip out, and a recipient's mail gateway may well remove an attachment or quarantine the whole document. If the attached file is essential, say so on the page as well, so the reader knows to look for it.
Every file you add is read from disk in your browser and written into the PDF locally. Nothing is uploaded - not the carrier, and not the possibly rather more sensitive spreadsheet you are attaching to it.
What this tool cannot do
- Reader support varies. Acrobat and Preview show attachments in a side panel, some readers hide them behind a menu, and a few browser viewers ignore them entirely - so a document whose attachment is essential should say so on the page.
- The attached bytes are added to the PDF, so the result is about the size of the original plus the size of everything you attach. Attachments are also frequently stripped by mail gateways and document management systems.
Questions people ask
- What kinds of file can I attach?
- Any of them. Spreadsheets, images, CSVs, ZIPs, Word documents, another PDF - the format places no restriction on what an embedded file contains. You can add up to 20 files in one pass, and the tool will warn rather than refuse if one is large enough to be a problem for your device's memory.
- Will the person I send it to see the attachment?
- In Acrobat and Preview, yes - there is an attachments or paperclip panel down the side. Some readers put it behind a menu, and a few in-browser viewers ignore embedded files completely, showing the pages and nothing else. Because of that, mention the attachment in the document itself if it matters, rather than relying on the recipient noticing a panel.
- How much bigger will my PDF get?
- Roughly the size of what you attach. The bytes are compressed on the way in, so a text-heavy CSV may shrink considerably and a JPEG or a ZIP will not shrink at all. Nothing about the pages changes, so running Compress PDF afterwards will reduce the document but not the attachment.
- How do I get rid of attachments in a file someone sent me?
- Sanitise PDF removes embedded files along with the other things a PDF can carry that are not pages - JavaScript, launch actions, embedded media. If you only want to swap the attachments for different ones, drop the file here and turn on the option to replace what is already embedded.
- Are the files I attach uploaded?
- No. Both the carrier and everything you attach are read locally and combined in a Web Worker in your browser. This is one of the tools where that matters most in practice, since the file being attached is often the underlying data that the PDF was written to summarise.