The fastest way depends on what you're starting with

If you have Word documents, images, or PDFs scattered across your computer and need them in a single file, the method changes based on what program you already have open. Most people can do this without buying anything — Windows and Mac both include free tools, and free online converters work if you prefer not to install software. The trade-off is speed versus privacy: desktop tools keep your files on your computer, while online tools are faster but send your documents to someone else's server.

The simplest route for most people is to use the document editor you already have. If you work in Microsoft Word, Google Docs, or a free alternative like LibreOffice, each one has a built-in way to insert other files into a single document, then export the result as PDF. If you're starting with PDFs that need combining, a dedicated PDF tool is faster than converting back to a document editor first.

Key Takeaways

  • Microsoft Word, Google Docs, and LibreOffice can all insert multiple documents into one file, then export as PDF — no separate tool needed.
  • If you're combining PDFs specifically, free desktop tools like PDFtk or online tools like Smallpdf are faster than opening each PDF in a document editor.
  • Online tools are quickest but upload your files to their servers; desktop tools keep everything on your computer but take a few more steps.
  • The file size of your final PDF depends on whether you're combining text documents or image-heavy files — images compress less than text.

Combining documents in Word, Google Docs, or LibreOffice

If your source files are Word documents, Google Docs, or a mix of formats, the fastest route is to open your document editor and insert the other files directly. In Microsoft Word, go to Insert, then Object, then Text from File — this pulls the content of another document into your current one. You can repeat this for as many documents as you need. Once everything is in one file, go to File, then Save As, and choose PDF as the format.

Google Docs works similarly but with a different menu path. Open a new Google Doc, then go to File, then Open, and select "Upload" to bring in a Word document or other file. Google will convert it to a Doc automatically. Then use Insert, then File, then Upload from Computer to add more documents. When you're done, go to File, then read, and choose PDF.

LibreOffice (the free alternative to Word) uses Insert, then File, to add other documents. The process is nearly identical to Word. Once everything is combined, export as PDF through File, then Export as PDF. All three of these methods keep your files on your computer the entire time, which matters if your documents contain sensitive information.

Combining PDFs with dedicated tools

If you're working with PDFs that are already in their final form, using a document editor to combine them is slower than using a tool built for the job. PDFtk (free, desktop software for Windows and Mac) lets you drag and drop multiple PDFs into a window, arrange them in order, and export a single combined file in seconds. read it from pdftk.com, install it, and you have a tool that works offline and keeps everything on your computer.

If you prefer not to install anything, Smallpdf.com and ILovePDF.com both let you upload multiple PDFs, arrange them, and read the combined result. These are faster than the document editor method because they're designed specifically for PDF work. The trade-off is that your files travel to their servers during the process. Both sites claim to delete files after a few hours, but if your PDFs contain confidential information, a desktop tool like PDFtk is the safer choice.

For Mac users specifically, Preview (the built-in image and PDF viewer) can combine PDFs without any additional software. Open the first PDF in Preview, then go to Edit, then Insert, then Page from File, and select the other PDFs in order. Save the result as a new PDF. This is free and keeps everything on your computer.

Combining images and mixed file types

If you're combining screenshots, photos, or scanned pages alongside documents, the process depends on whether your images are already in a document or still separate files. If they're separate, the fastest route is to create a new document in Word or Google Docs, then insert all the images and documents in the order you want them. Arrange them on the page, then export as PDF.

For scanned pages specifically, many scanner apps (like Microsoft Lens or Adobe Scan) let you capture multiple pages and save them as a single PDF automatically. If you've already scanned pages separately, you can use the same PDF combining tools mentioned above — PDFtk, Smallpdf, or Preview on Mac — to merge them into one file.

Managing file size when combining documents

The final PDF size depends on what you're combining. Text documents compress very small — a 50-page Word document usually becomes a 1 to 2 MB PDF. Images and scanned pages are much larger: a single scanned page can be 2 to 5 MB depending on resolution. If you're combining many scanned documents and the file becomes too large to email or upload, you have two options: reduce the image quality when scanning (most scanner apps let you choose resolution), or use a compression tool like Smallpdf's compress feature to shrink the final PDF.

When you export a document as PDF from Word or Google Docs, you usually get a choice of quality settings. Choosing "Standard" instead of "High Quality" reduces file size without making the text unreadable. For PDFs that are mostly text, this rarely matters — the file stays small either way. For image-heavy PDFs, the quality setting makes a significant difference.

Keeping your documents in the right order

When you insert documents into Word or Google Docs, they appear in the order you insert them. If you need to rearrange them later, you can cut and paste sections within the document before exporting as PDF. With dedicated PDF tools like PDFtk or Smallpdf, you can drag and drop the files into the order you want before combining them — this is usually faster than rearranging after the fact.

If you're combining many documents and want to keep track of what goes where, create a straightforward numbered list first: Document 1 (Introduction.docx), Document 2 (Chapter 1.docx), and so on. Then insert or upload them in that order. This prevents mistakes and saves time if you need to redo the combination later.

Frequently Asked Questions

Can I combine PDFs that have different page sizes?

Yes. PDFtk, Smallpdf, and Preview all handle mixed page sizes without problems — they straightforward place each PDF as-is into the combined file. The result will have pages of different sizes, which is fine for most uses. If you need all pages to be the same size, you would need to resize them first, which requires more specialized software.

What if I want to combine documents but keep them as separate sections?

In Word and Google Docs, you can insert page breaks between documents so each one starts on a new page. In Word, go to Insert, then Page Break, between each document you insert. In Google Docs, press Ctrl+Enter (or Cmd+Enter on Mac) to create a page break. This keeps the content separate visually while still being one PDF file.

Do I need to convert my documents to PDF before combining them?

No. Word, Google Docs, and LibreOffice can all combine documents in their native formats (like .docx or .odt) and export the result as PDF in one step. You only need to convert to PDF first if you're using a dedicated PDF tool like PDFtk, which works with PDFs specifically.

Is it safe to use online PDF tools with confidential documents?

Online tools like Smallpdf and ILovePDF are generally safe, but they do upload your files to their servers. If your documents contain sensitive information, a desktop tool like PDFtk or your document editor's export function keeps everything on your computer. Check the tool's privacy policy if you're unsure.

Can I combine documents on my phone or tablet?

Yes, but it's slower than on a computer. Google Docs works on phones and tablets and can combine documents the same way as the desktop version. For PDFs specifically, apps like Adobe Acrobat Reader (free version) can combine PDFs on iPad, but Android options are more limited. For most people, doing this on a computer is faster.