The PDF was designed so that a document looks the same on every device and printer. That reliability is why governments, universities and companies ask for PDFs. It also means PDFs are the file type people most often need to combine, shrink, print and convert. This handbook covers the tasks you are likely to face and the pitfalls on each.

What is inside a PDF

A PDF is a set of pages described with text, vector drawings and images, plus the fonts they need. A PDF created from a word processor is mostly text and vectors, so it is small and sharp at any zoom. A PDF made from a scan is a stack of pictures, one per page, so it is much larger and, without text recognition, cannot be searched or copied.

Merging PDFs

Merging means placing the pages of several PDFs one after another in a single file. Doing it well is mostly about order and preservation:

  • Order. Arrange files exactly as the reader should meet them. Cover letter, then CV, then certificates is typical for applications.
  • Preservation. A good merge copies the original pages without re-rendering them, so text stays selectable and images keep their resolution. Be wary of tools that convert pages to pictures.
  • Bookmarks. A bookmark per source file lets readers jump between sections of a long merged document.
  • Password protection. Encrypted PDFs usually must be unlocked before merging; you will need the password.

With the PDF Merger you add files, reorder them with arrows or drag and drop, and download one combined PDF.

Printing several pages per sheet (N-up)

N-up printing places 2, 4, 6, 8 or 16 pages on each sheet, reducing paper use and making compact reading copies. Which layout works depends on the content:

  • 2 per sheet keeps text comfortably readable; ideal for articles and reports.
  • 4 per sheet suits lecture slides and drafts. Body text becomes small, but headings remain clear.
  • 6 per sheet is the classic handout layout for presentations.
  • 8 per sheet is best for thumbnails, quick reviews and contact-sheet style overviews.

Choose the paper your printer actually holds: A4 in most countries, Letter in the United States and Canada. Printing double-sided doubles the saving. A thin border around each page makes the boundaries obvious when several pages share a sheet.

Why a PDF is large, and what to do about it

  • High-resolution images. Photos at 300 dpi or more are usually far above what a screen needs. Reducing image resolution is the biggest saving.
  • Scanned pages saved as colour. Text documents scanned in colour at high resolution are huge; scanning in grey or black and white at 150 to 200 dpi is usually enough for reading.
  • Embedded fonts and duplicated content. These add a little; an optimiser can remove duplicates.
  • Attachments and metadata. Occasionally PDFs carry embedded files.

If the document is a collection of scanned pages, a practical approach is to compress each page image first with the File Size Reducer, then assemble them into a PDF with Image to PDF.

Turning pictures and slides into PDFs

Photographs and scans can be placed one per page, or several per sheet, using Image to PDF. Presentations are converted page by page with the PPT Merger, which can also lay out 2, 4, 6, 8 or 16 slides per page for handouts. Slides are rendered as vector pages, so text stays crisp.

Searchable and copyable text

A scanned PDF becomes useful when it has a text layer that was produced by optical character recognition. That lets you search a long document, select a paragraph and paste it elsewhere. Our OCR guide explains how it works and how to get accurate results.

Submitting PDFs to portals

  • Check the size limit and stay comfortably under it.
  • Use simple file names without spaces or special characters.
  • Open the final file and scroll through every page before uploading.
  • Avoid password protection unless you were asked for it.
  • Prefer one combined PDF in the requested order over many small ones.

Summary

For a clean result: keep originals, merge in the order a reader needs, preserve text instead of flattening it, print several pages per sheet only when the text remains legible, and compress images rather than whole documents. Following those rules keeps your PDFs small, sharp and professional.

Accessibility and metadata

A PDF built from real text is accessible to screen readers; a PDF built from scans is not unless it has a text layer. Document properties such as title and author are stored inside the file and may reveal more than you intend, for instance the name of the machine or the software used. Before publishing, check the properties and remove anything you do not want public.

Signing and form-filling

Filling in a PDF form usually means typing into form fields, which are stored in the file. Flattening afterwards turns the filled fields into page content so nobody can change them accidentally. Digital signatures are a separate cryptographic feature; merging or editing a signed PDF invalidates the signature, so merge first and sign last.

Troubleshooting

  • Pages are the wrong size. Source files may mix A4, Letter and custom sizes. Choose a paper size when merging so every page is fitted onto the same sheet.
  • Text looks blurry. The page was a scan or screenshot. Re-scan at a higher resolution, or run text recognition.
  • The file will not open after merging. One of the inputs was damaged. Open each source separately to find it.
  • Landscape pages print sideways. Check the printer's orientation setting; N-up layouts pick the best grid automatically.
  • The merged file is huge. Images are the cause; reduce them before assembling.