Plan the steps needed to use overlay PDF pages in five stages: validate two local PDFs, choose the page mapping, set opacity from 0.1 to 1, create the new file, and inspect every important page.
Overlaying is a visual foreground operation rather than a general document merge. The base PDF controls the output page count, page order, page boxes, and underlying content, while the overlay PDF supplies artwork drawn on top. Your plan should therefore identify the controlling document, explain how the foreground pages should match, and define how you will verify the result.
Use PDF Overlay for prepared letterhead, borders, stamp sheets, transparent design layers, or corresponding foreground pages. These are visual-combination tasks that fit the tool’s page-mapping and proportional-centering model.
Define the result before choosing files
Start by deciding what the finished PDF must contain. A one-page foreground repeated across a report has different requirements from a multi-page overlay designed to match selected report pages. Record the expected result before opening the tool so that each later decision has a clear purpose.
| Planning decision | Supported choice | Why it matters |
|---|---|---|
| Base document | The PDF whose page count, order, boxes, and underlying content should control the output | This prevents a visually useful layer from being applied to the wrong document |
| Overlay structure | One reusable page or multiple pages mapped one to one | The overlay page count determines the matching behavior |
| Opacity | A value from 0.1 to 1 | It changes the visibility of the foreground artwork |
| Verification | Inspection of every important output page | It helps reveal mapping errors, hidden content, and readability problems |
Before proceeding, write down four items:
- The exact base PDF and its required final page order.
- Whether the foreground should repeat or correspond to individual pages.
- The opacity needed to keep the combined design readable.
- The pages you will inspect after downloading, including the first, last, and representative middle pages.
Prepare and run the overlay workflow
- Choose the base PDF. This is the document whose page count, page order, page boxes, and underlying content should remain in control. Confirm that this is the correct file before adding any foreground artwork.
- Choose the overlay PDF. Select the local file containing the layer you want to place above the base. Both files must be non-empty PDFs, and each must be no larger than 25 MiB. Encrypted, damaged, unsupported, oversized, and incorrectly labeled files produce a visible error; password protection is not bypassed.
- Check the page mapping. If the overlay contains exactly one page, prepare for that page to repeat on every base page. If it contains multiple pages, check that page 1 corresponds to base page 1, page 2 to base page 2, and so forth.
- Set the overlay opacity. Choose a value from 0.1 to 1. A value of 1 applies the layer at full opacity, while smaller accepted values make it more transparent where the PDF graphics model supports that effect.
- Select Overlay PDFs. The browser embeds the overlay pages into the base document, fits each applied layer proportionally, centers it, and creates a new PDF copy. Neither input nor the generated output is uploaded to Lizely.
- Download the combined PDF. The new file uses the base filename with -overlay added before the PDF extension. The original base and overlay files are not overwritten.
- Inspect every important page. Confirm the page count, expected mapping, placement, and readability before sending, sharing, or printing the result. Look closely at pages with dense base content and pages carrying dark or mostly opaque layers.
Match overlay pages to base pages
Page mapping is fixed by the number of pages in the overlay PDF. There is no separate rule to configure during creation, so verify the files before selecting the final opacity. A longer explanation of how overlay pages are matched to base pages can help when deciding which file belongs in each slot.
| Overlay PDF | Matching rule | Expected output |
|---|---|---|
| Exactly one page | The single overlay page repeats on every base page | Every page receives the same centered foreground layer |
| More than one page | Overlay page 1 maps to base page 1, page 2 to base page 2, and so on | Matching pages receive their corresponding overlay pages |
When the multi-page overlay is shorter than the base, base pages beyond the overlay count remain unchanged. When it is longer, overlay pages beyond the base count are ignored. The base still determines the final page count.
This distinction matters for reusable designs. Letterheads, borders, and stamp sheets usually work well as a single-page overlay, while a prepared foreground sheet for each report page depends on correct one-to-one ordering. If the overlay pages contain several designs, confirm their sequence before processing them.
Plan for centered, proportional placement
Each applied overlay page is scaled uniformly to fit inside its corresponding base page. The aspect ratio is preserved, and the fitted layer is centered horizontally and vertically without cropping or stretching. If the two documents use different page shapes, blank space can remain on two sides of the smaller fitted area.
The tool does not provide fill-and-crop behavior, arbitrary offsets, rotation controls, alignment corners, or separate scaling for width and height. Plan for automatic centering rather than expecting to drag or align the layer manually. If an overlay must cover the base edge to edge, prepare it with a compatible page shape; the tool cannot stretch or crop it to force full coverage.
Set opacity around the review copy
Choose opacity with both the base artwork and foreground design in mind. Overlay content is drawn afterward, so opaque portions appear above the existing page artwork. Existing transparency inside the overlay PDF remains part of that embedded artwork, and lower opacity changes the drawing operation rather than removing any layer.
A full-page opaque design can hide the base completely, while a dark layer can reduce readability even when it is partly transparent. Start with the lowest opacity that still serves the design’s purpose, then review the actual result. Visual concealment is not secure redaction: covered content remains in the base content stream and can still be present beneath the overlay.
Create, download, and verify the new PDF
The output preserves the base as the structural document and adds the overlay as embedded PDF artwork rather than a screenshot. Vector content and text can remain vector-based to the extent supported by the underlying PDF library. Interactive objects such as links, comments, form fields, scripts, attachments, and outline destinations are not carried across as equivalent interactive objects, so treat the result as a visual combination.
If you change either input or the opacity, the previous download is invalidated: its object URL is revoked and the obsolete download is removed. A stale job also cannot replace results made from newer choices or settings. Regenerate the file after any change instead of relying on an earlier download.
Use a structured review for the finished document:
- Compare the output page count with the base PDF.
- Check that every intended page received the correct overlay.
- Confirm the layer is centered, proportional, and not cropped.
- Read the base and foreground together to catch low-contrast combinations.
- Inspect important pages at normal viewing size and use a printed proof for print-critical work.
The guide to checking a PDF overlay result provides a focused review sequence for these visual and structural checks.
Plan around the tool’s limits
PDF Overlay produces a visual layer, not a semantic merge of every document structure. It does not concatenate, reorder, redact, certify, or flatten the base document. It also does not inspect blend modes, knockouts, overprint settings, spot colors, or printing separations, so print-critical files require professional preflight. A signature-looking image placed in an overlay does not create a cryptographic digital signature or establish signer identity.
Choose a different workflow when the required operation is not visual layering. Use Merge PDF to concatenate documents in a chosen order, Alternate Mix PDF to interleave pages, Add Watermark to PDF for generated text marks, or Sign PDF for a drawn signature workflow. If your goal is to conceal sensitive information permanently, use a proper redaction process rather than an opaque overlay.
A reliable plan keeps the base document fixed, confirms whether the foreground repeats or maps one to one, chooses opacity with readability in mind, and reserves time for page-by-page inspection. That sequence produces a predictable combined PDF while keeping the limitations of visual overlay visible throughout the process.